How many observations are required to be 90% sure of being within ±2.5% (i.e., an error) of the population mean for an activity, which occurs 30% of the time? How many more observations need to be taken to increase one’s confidence to 95% certainty?

Answers

Answer 1

We would need 453 more observations to increase your confidence level to 95% certainty.

To determine the required number of observations to be 90% sure of being within ±2.5% of the population mean for an activity occurring 30% of the time, we'll use the sample size formula for proportions:

n = (Z^2 * p * (1-p)) / E^2

Here, n is the sample size, Z is the z-score corresponding to the desired confidence level, p is the proportion (30% or 0.30), and E is the margin of error (±2.5% or 0.025).

For a 90% confidence level, the z-score (Z) is 1.645. Plugging the values into the formula:

n = (1.645^2 * 0.30 * (1-0.30)) / 0.025^2
n ≈ 1023.44

So, you would need approximately 1024 observations to be 90% sure of being within ±2.5% of the population mean.

To increase the confidence level to 95%, the z-score (Z) changes to 1.96. Using the same formula:

n = (1.96^2 * 0.30 * (1-0.30)) / 0.025^2
n ≈ 1476.07

So, you would need approximately 1477 observations for a 95% confidence level.

To find the additional number of observations needed, subtract the initial sample size from the new sample size:

1477 - 1024 = 453

Therefore, you would need 453 more observations to increase your confidence level to 95% certainty.

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Related Questions

A school district wants to identify factors that may be affecting how well the students are doing based on their grade point averages. Which statistical method would be best to use in this situation

Answers

Multiple regression analysis assumes certain underlying statistical assumptions are met, such as linearity, independence of errors, homoscedasticity, and normally distributed errors.

A statistical method that would be best to use in this situation is Multiple Regression Analysis.

Multiple Regression Analysis is a statistical method used to identify the relationships between a dependent variable and multiple independent variables.

The dependent variable is the grade point average (GPA) of students, and the independent variables are the factors that may be affecting how well the students are doing.

Multiple regression can be used to model the relationships between these variables and to identify which factors are most strongly associated with differences in GPA.

Multiple regression analysis is a useful tool for exploring the complex relationships between multiple variables and can help identify which factors are most important in predicting GPA.

By analyzing the relationships between the various independent variables and GPA, school districts can identify areas where they may need to focus their efforts to improve academic performance.

It's also important to use caution when interpreting the results of regression analysis, as correlation does not necessarily imply causation, and other factors not included in the model may also be influencing GPA.

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A survey among freshmen at a certain university received that the number of hours spent studying the week before final exams was normally distributed with mean 25 and standard deviation 7. Round your answers to nearest hundredth. (e.g. 0.345 would be entered as 0.35) (a) Find the 98th percentile of the number of hours studying.

Answers

The 98th percentile of the number of hours spent studying the week before final exams is approximately 39.35 hours.

The 98th percentile of the number of hours spent studying the week before final exams, assuming a normal distribution with mean 25 and standard deviation 7, can be calculated using the standard normal distribution table.

To find the z-score corresponding to the 98th percentile, we use the formula:

z = (x - μ) / σ

where x is the value at the 98th percentile, μ is the population mean, and σ is the population standard deviation.

Using a calculator, we find that the z-score corresponding to the 98th percentile is approximately 2.05.

To find the value of x at the 98th percentile, we rearrange the formula as:

x = μ + zσ

Substituting the given values, we get:

x = 25 + 2.05 × 7 ≈ 39.35

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Which point is a point where the graph of y = (x + 2)(x2 + 4x + 3) crosses the x-axis?

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The points at which the graph of  y = (x + 2)(x² + 4x + 3) crosses the x-axis are: (-1, 0), (-2, 0) and (-3, 0)

Consider an equation of the graph y = (x + 2)(x² + 4x + 3)

We need to find the points at wchi the graph of function y = (x + 2)(x² + 4x + 3)  crosses the x-axis.

We know that the x-intercept if nothing ut the point at whhich the graph of the function crosses the x-axis.

To find the x-intercept of the graph we need to solve an equation y = 0

Consider  y = 0

(x + 2)(x² + 4x + 3) = 0

x + 2 = 0    OR   x² + 4x + 3 = 0

x = -2      OR      (x + 1)(x + 3) = 0

x = -2      OR       x = -1         OR       x = -3

Thus the required points are x = -1, -2 and -3

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what happens to an inequality sign when the inequality is multiplied or divided by a negative number

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When an inequality is multiplied or divided by a negative number, the inequality sign will flip, meaning it will change its direction. For example, if you have a > b and you multiply or divide both sides by a negative number, the inequality will become a < b. This is because the relationship between the values reverses when multiplied or divided by a negative number.

Explanation:

When an inequality is multiplied or divided by a negative number, the direction of the inequality sign is flipped. This is because multiplication or division by a negative number, results in a reversal of the order of the numbers on the number line.

To see why this happens, consider the following example:

Suppose we have the inequality x < 5. If we multiply both sides of this inequality by -1, we get -x > -5. Notice that we have flipped the inequality sign from "<" to ">". This is because multiplying by -1 changes the sign of x to its opposite, and also changes the sign of 5 to its opposite, resulting in a reversal of the order of the numbers on the number line.

Similarly, if we divide both sides of the inequality x > 3 by -2, we get (-1/2)x < (-3/2). Here, we have again flipped the inequality sign from ">" to "<". This is because dividing by a negative number also changes the order of the numbers on the number line.

In general, if we have an inequality of the form a < b or a > b, where a and b are real numbers, and we multiply or divide both sides by a negative number, we obtain:

If we multiply by a negative number, the inequality sign is flipped. For example, if a < b and c < 0, then ac > bc.

If we divide by a negative number, the inequality sign is also flipped. For example, if a > b and c < 0, then a/c < b/c.

Therefore, it is important to be mindful of the signs of the numbers involved when performing operations on inequalities. If we multiply or divide by a negative number, we must flip the direction of the inequality sign accordingly.

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3. If the parents have two children without the disorder, what is the probability that their third child will have cystic fibrosis

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Cystic fibrosis is an autosomal recessive genetic disorder. This means that in order for a child to have cystic fibrosis, both parents must be carriers of the recessive gene.

When both parents are carriers, the probability for each child to inherit the disorder is as follows:

1. 25% chance of having cystic fibrosis (inheriting two copies of the recessive gene)
2. 50% chance of being a carrier (inheriting one copy of the recessive gene)
3. 25% chance of not being a carrier or having the disorder (inheriting no copies of the recessive gene)

Since the question states that the first two children do not have cystic fibrosis, this does not affect the probability of the third child having cystic fibrosis. The probability remains the same for each pregnancy.

Therefore, the probability of the third child having cystic fibrosis is still 25%. It's important to note that the probabilities are independent for each child, meaning the outcome of one child's genetic inheritance does not influence the outcome for another child.

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PLEASE ANSWER ASAP
Drag and drop to complete the proof below:

Given: DE←→
is tangent to circle C, at point F

Prove: ∠FEC and ∠ECF are complementary

Answers

The proof for each theorem is matched as;

<EFC is a right angle: Definition of a right angle

m<EFC = 90; Definition of a tangent line

m<EFC + m<FEC + m<ECF = 180 degrees; triangle sum theorem

90 + m<FEC + m<ECF = 180; substitution property of equality

m<FEC + m<ECF = 90; substitution property of equality

m<FEC + m<ECF = definition of complementary angles

How to determine the corresponding proofs

To determine the values, we need to know the following;

The sum of the angles in a triangle is equal to 180 degrees according the the triangle sum theorem.Complementary angles are pair of angles that sum up to 90 degrees.The angles at right angle is 90 degreesAngles on a straight line is 180 degrees

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When a research hypothesis does not predict the direction of a relationship, the test is ______. Group of answer choices direct positive one-tailed two-tailed

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When a research hypothesis does not predict the direction of a relationship, the test is typically two-tailed.

A two-tailed hypothesis is used when there is no specific prediction about

the direction of the relationship between variables.

It simply states that there is a relationship between the variables being

studied, but does not specify whether the relationship will be positive or

negative.

In contrast, a one-tailed hypothesis predicts the direction of the

relationship (i.e. positive or negative) and is used when there is a clear

expectation about the direction of the effect. A direct positive hypothesis

predicts a positive relationship between variables.

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Assume the conditions of the linear model hold. A 95% confidence interval for will be constructed. What is the margin of error

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The margin of error for a 95% confidence interval for the population mean (μ) is given by: Margin of Error = z*(σ/√n)

where z is the critical value from the standard normal distribution for a 95% confidence level (z = 1.96), σ is the population standard deviation (which is usually unknown and estimated by the sample standard deviation, s), and n is the sample size.

Assuming the conditions of the linear model hold, the margin of error for a 95% confidence interval for the population mean can be calculated using the above formula.

Note that the linear model assumptions include that the errors are normally distributed, the mean of the errors is zero, and the variance of the errors is constant.

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Kareem is trying to decide which college to attend full time next year. Kareem believes there is a 55% chance that he will attend State College and a 33% chance that he will attend Northern University. The probability that Kareem will attend either State or Northern is (state your answer as a decimal and round your answer to two decimal places).

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The probability that Kareem will attend either State or Northern is 0.88, which is 88% as a percentage. Rounded to two decimal places, the answer is 0.88.

The probability that Kareem will attend either State or Northern is the sum of the individual probabilities of attending each college.

Probability is a measure of the likelihood or chance of an event occurring. It is usually expressed as a number between 0 and 1, where 0 indicates that an event is impossible and 1 indicates that an event is certain.

The probability of an event A is calculated as the number of outcomes that result in A divided by the total number of possible outcomes. This is known as the classical definition of probability.

P(State or Northern) = P(State) + P(Northern) = 0.55 + 0.33 = 0.88

So the probability that Kareem will attend either State or Northern is 0.88, which is 88% as a percentage. Rounded to two decimal places, the answer is 0.88.

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What is the chance of drawing two Jacks one after another, when drawing without replacement from an incomplete deck of 48 cards that contains 4 Jacks

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The chance of drawing two Jacks one after another, when drawing without replacement from an incomplete deck of 48 cards that contains 4 Jacks, is [tex]\frac{1}{188}[/tex]

The chance of drawing two Jacks one after another, when drawing without replacement from an incomplete deck of 48 cards that contains 4 Jacks, can be calculated using the following steps:

Step 1: Find the probability of drawing the first Jack.
There are 4 Jacks in the 48-card deck, so the probability of drawing the first Jack is [tex]\frac{4}{48}[/tex].

Step 2: Find the probability of drawing the second Jack.
After drawing the first Jack, there are now 3 Jacks left in the deck and only 47 cards remaining. The probability of drawing the second Jack is now [tex]\frac{3}{47}[/tex].

Step 3: Multiply the probabilities from steps 1 and 2 to find the overall probability of drawing two Jacks one after another.
[tex](\frac{4}{48}) (\frac{3}{47} ) = \frac{12}{2256}[/tex]

Step 4: Simplify the probability.
The simplified probability of drawing two Jacks one after another is [tex]\frac{1}{188}[/tex] .

Therefore, the chance of drawing two Jacks one after another, when drawing without replacement from an incomplete deck of 48 cards that contains 4 Jacks, is 1/188.

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what is the value of b

Answers

√2 is the value of the side b.

In the given triangle from the sine rule,

sin60/a = sin90/2√2 = sin 30/b

Thus,

1/2√2 =1/2/b

b = √2

Therefore, the value of b is √2.

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The ogre under the bridge eats 4/5 of a pizza and then throws the rest of the pizza to the rats. The rats eat 3/4 of what is left. What fraction of the pizza is left when the rats are done

Answers

Therefore, the fraction of the pizza left when the rats are done is 1/20.

we need to first find out how much of the pizza is left after the ogre eats 4/5 of it. We can do this by subtracting 4/5 from 1 (the whole pizza) to get 1/5.
Then, we need to find out how much of that 1/5 is left after the rats eat 3/4 of it. To do this, we can multiply 1/5 by 1/4 (since the rats ate 3/4, that means they left 1/4 of what was left) to get 1/20.
The ogre under the bridge eats 4/5 of the pizza, leaving 1/5 of the pizza left. Then, the rats eat 3/4 of what is left, which is 1/5. We can find out how much of that 1/5 is left by multiplying it by 1/4 (since the rats ate 3/4), which gives us 1/20. Therefore, the fraction of the pizza left when the rats are done is 1/20.

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A professor of linguistics refuses the claim that the average student spends 3 hours studying for the midterm exam. She thinks they spend more time than that. Which hypotheses are used to test her claim

Answers

Based on the information provided, two hypotheses could be used to test the professor's claim that students spend more than 3 hours studying for the midterm:

1) Null hypothesis (H0): The average number of hours students spend studying for the midterm exam is 3.
This matches the initial claim that the professor disputes. The null hypothesis will be rejected if there is evidence that the average is greater than 3 hours.

2) Alternative hypothesis (Ha): The average number of hours students spend studying for the midterm exam is greater than 3.
This hypothesis is consistent with the professor's claim that students study for longer than 3 hours on average. For the alternative hypothesis to be supported, the results must show an average of over 3 hours.

Some additional notes on the hypotheses:

• The null hypothesis reflects the initial claim that will be tested. The alternative hypothesis provides the alternative explanation that will be accepted if the null hypothesis is rejected.

• "3" in the null hypothesis and "greater than 3" in the alternative hypothesis represent the critical values that determine whether the hypotheses are supported or rejected.

• A one-tailed test will be used since only one direction (greater than) is being tested. The alternative hypothesis provides only one side of the comparison.

• The null hypothesis proposes an equals relation while the alternative hypothesis proposes a greater than relation. They represent opposite possibilities.

• Statistical analysis of the data will determine whether there is enough evidence to reject the null hypothesis in favor of the alternative hypothesis. The alternative will be accepted if the null is rejected.

• For the alternative hypothesis to be supported, the average number of hours studying would need to be statistically significantly greater than 3. Just being greater than 3 may not be enough to reject the null hypothesis.

Does this help explain the hypotheses and key points regarding testing the professor's claim? Let me know if any part of the explanation is unclear or if you have additional questions! I can also help explain statistical hypothesis testing in more detail if needed.

The goals are:
1) Identify the null and alternative hypotheses consistent with what is being tested
2) Ensure they reflect opposite possibilities (average=3 vs. average>3 hours)
3) Determine the critical values that will indicate whether a hypothesis is supported or rejected
4) Explain how the statistical analysis will allow us to decide between the hypotheses

Please let me know if you have any other questions! I'm happy to help further explain any part of the concepts or steps.

9. A university requires its biology majors to take a course called BioResearch. The prerequisite for this course is that students must have taken either a statistics course or a computer programming course. By the time they are juniors, 52% of the biology majors have taken statistics, 23% have taken computer programming, and 7% have taken both. a) What percent of junior biology majors are eligible to take BioResearch

Answers

By the time they are juniors, 52% of the biology majors have taken statistics, 23% have taken computer programming, and 7% have taken both. 68% of junior biology majors are eligible to take BioResearch

To be eligible to take BioResearch, a student must have taken either a statistics course or a computer programming course. From the given information, we know that 52% of junior biology majors have taken statistics and 23% have taken computer programming. However, we need to account for the fact that some students may have taken both courses.
To do this, we can use the formula:
Total = A + B - Both
where A represents the percentage of students who have taken statistics, B represents the percentage of students who have taken computer programming, and Both represents the percentage of students who have taken both courses.
Plugging in the values we have:
Total = 52 + 23 - 7
Total = 68
Therefore, 68% of junior biology majors are eligible to take BioResearch.

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linear equation thats a horizontal line on a graph example

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An example of a linear equation that represents a horizontal line is expressed as: y = 1.

What is the Linear Equation of a Horizontal Line?

The linear equation that represents a horizontal line is expressed as y = b, where the value of b is the point on the x-axis where the line intercepts the y-axis horizontal line. The point is on the line is (0, b).

An example of a graph that shows a horizontal line is attached below where the line cuts the y-axis at (0, 1).  Thus, the linear equation is expressed as y = 1.

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According to the previous (Part 4) multivariate regression model that you have created using three independent variables: weekend, school break, and weather as predictors of the shaped ski rentals, which is the value of the intercept?

Answers

The intercept is an essential component of the regression model, as it helps to establish a baseline prediction for the number of shaped ski rentals before accounting for the effects of the independent variables.

Based on the previous multivariate regression model that used weekend, school break, and weather as predictors of shaped ski rentals, the value of the intercept refers to the estimated number of shaped ski rentals when all independent variables are equal to zero.

In this case, the intercept would represent the expected number of shaped ski rentals on a weekday during a non-school break period when the weather is average. Unfortunately, without the exact equation for the regression model, it's impossible to determine the specific value of the intercept.

However, it is important to note that the intercept is an essential component of the regression model, as it helps to establish a baseline prediction for the number of shaped ski rentals before accounting for the effects of the independent variables.

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Evaluate the line integral / (+ +4vY) ds, where C is the path going counterclock- > > wise around the square with vertices (0,0), (2,0), (2, 2) and (0,2). Show all your work. Important: Make sure to realize that we are not talking of a line integral in a vector field here. Also, A regular line integral share the property that line integral in a vector have when C is the union of curves.

Answers

The  value of the line integral / (+ +4vY) ds, where C is the path going counterclockwise around the square with vertices (0,0), (2,0), (2,2) and (0,2), is 32v.

To evaluate the line integral, we need to parameterize the square and then compute the line integral along each of the four sides.

Let's parameterize the square as follows:
- For the bottom side from (0,0) to (2,0), we can use the parameterization r(t) = <t, 0>, where 0 ≤ t ≤ 2.
- For the right side from (2,0) to (2,2), we can use the parameterization r(t) = <2, t>, where 0 ≤ t ≤ 2.
- For the top side from (2,2) to (0,2), we can use the parameterization r(t) = <t, 2>, where 0 ≤ t ≤ 2.
- For the left side from (0,2) to (0,0), we can use the parameterization r(t) = <0, t>, where 0 ≤ t ≤ 2.

Now we can compute the line integral along each of these sides and add them up to get the total line integral.

Line integral along the bottom side:
- r(t) = <t, 0>, where 0 ≤ t ≤ 2.
- dr/dt = <1, 0>.
- ds/dt = ||dr/dt|| = 1.
- (+4vY) ds = 4v(0) ds = 0.
- Integral from t=0 to t=2: 0 dt = 0.

Line integral along the right side:
- r(t) = <2, t>, where 0 ≤ t ≤ 2.
- dr/dt = <0, 1>.
- ds/dt = ||dr/dt|| = 1.
- (+4vY) ds = 4v(t) ds = 4v(t) dt.
- Integral from t=0 to t=2: 4v(t) dt = 8v.

Line integral along the top side:
- r(t) = <t, 2>, where 0 ≤ t ≤ 2.
- dr/dt = <1, 0>.
- ds/dt = ||dr/dt|| = 1.
- (+4vY) ds = 4v(2) ds = 8v ds = 8v.
- Integral from t=0 to t=2: 8v dt = 16v.

Line integral along the left side:
- r(t) = <0, t>, where 0 ≤ t ≤ 2.
- dr/dt = <0, 1>.
- ds/dt = ||dr/dt|| = 1.
- (+4vY) ds = 4v(t) ds = 4v(t) dt.
- Integral from t=0 to t=2: 4v(t) dt = 8v.

Adding up the line integrals along each side, we get:
- Total line integral = 0 + 8v + 16v + 8v = 32v.

Therefore, the value of the line integral / (+ +4vY) ds, where C is the path going counterclockwise around the square with vertices (0,0), (2,0), (2,2) and (0,2), is 32v.

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When determining the cell density of a sample by the standard plate count method, the final density of cells is reported as

Answers

When determining the cell density of a sample by the standard plate count method, the final density of cells is reported as colony forming units "(CFUs) per milliliter of sample."

This method involves diluting the sample and spreading it onto a solid agar medium, allowing the bacteria to grow and form visible colonies.

The number of colonies on the plate is then counted and multiplied by the dilution factor to determine the CFUs per milliliter of the original sample.It is important to note that the standard plate count method assumes that each colony originates from a single bacterial cell, and therefore, the number of colonies on the plate reflects the number of viable cells in the sample. However, not all bacteria may grow on the agar medium used in this method, and some may form clustered colonies or chains, leading to an underestimation of the cell density. Additionally, some bacteria may form spores that are resistant to heat and other environmental stresses, and may not be detected by this method.Despite these limitations, the standard plate count method remains a widely used and reliable method for determining cell density in many applications, including clinical microbiology, food and beverage production, and environmental monitoring.

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The cycle time for trucks hauling concrete to a highway construction site is uniformly distributed over the interval 40 to 85 minutes. What is the probability that the cycle time exceeds 75 minutes if it is known that the cycle time exceeds 45 minutes

Answers

The probability that the cycle time exceeds 75 minutes, given that it already exceeds 45 minutes, is 25%.


Given the information provided, we know the following:

1. The cycle time for trucks hauling concrete is uniformly distributed over the interval 40 to 85 minutes.
2. We need to find the probability that the cycle time exceeds 75 minutes, given that it already exceeds 45 minutes.

Step 1: Determine the length of the original interval.
The original interval is from 40 to 85 minutes, so the length is 85 - 40 = 45 minutes.

Step 2: Determine the length of the conditional interval.
Since we know that the cycle time already exceeds 45 minutes, our new interval starts at 45 minutes and ends at 85 minutes. The length of this interval is 85 - 45 = 40 minutes.

Step 3: Determine the length of the interval for cycle times exceeding 75 minutes.
The interval for cycle times exceeding 75 minutes starts at 75 and ends at 85, so the length of this interval is 85 - 75 = 10 minutes.

Step 4: Calculate the probability.
Since the cycle time is uniformly distributed, the probability is equal to the ratio of the lengths of the intervals:
Probability = (Length of interval for cycle times exceeding 75 minutes) / (Length of conditional interval)
Probability = 10 minutes / 40 minutes = 0.25 or 25%

So, the probability that the cycle time exceeds 75 minutes, given that it already exceeds 45 minutes, is 25%.

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A car salesman is told that he must make four sales each day. The salesman believes that if he visits with a customer the probability that the customer will purchases a car is 0.3. What is the expected number of customers that the salesman must visit to make his daily sales goal

Answers

The car salesman must visit approximately 14 customers to meet his daily sales goal of 4 cars, based on the given probability of 0.3.

To calculate the expected number of customers a car salesman must visit to achieve his daily sales goal, we can use the concept of probability. Given that the probability of a customer purchasing a car is 0.3, and the salesman needs to make 4 sales each day, we can use the formula:

Expected number of customers = (Number of sales needed) / (Probability of a successful sale)

In this case, the number of sales needed is 4, and the probability of a successful sale is 0.3. Plugging these values into the formula, we get:

Expected number of customers = 4 / 0.3 = 13.33

Therefore, the car salesman must visit approximately 14 customers (since we cannot have a fraction of a customer) to meet his daily sales goal of 4 cars, based on the given probability of 0.3. Keep in mind that this is an average value, and the actual number of customers required may vary from day to day.

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Tickets to a Broadway show cost $40 for adults and $25 for children. The total receipts for 1600 tickets at one performance were $56,050. How many adult and how many child tickets were sold

Answers

Answer:

Let a be the cost of an adult ticket and c be the cost of a child's ticket.

40a + 25c = 56,050--->40a + 25c = 56,050

a + c = 1600-------------->40a + 40c = 64,000

----------------------------

15c = 7,950

c = 530, a = 1,070

530 child tickets, 1,070 adult tickets

Weights (ounces) of 17 digital cameras are listed (chosen at random): 14 13 8 15 19 15 35 8 17 10 9 17 21 7 15 11 24 Assume the sample is from a normally distributed population. Construct the confidence intervals for the population variance. Use a 95% level of confidence.

Answers

Thus,  the 95% confidence interval for the population variance is (54.95, 1274.12) ounces^2. This means that we are 95% confident that the true variance of the population lies within this interval.

To construct the confidence interval for the population variance of the given sample, we can use the Chi-square distribution.

Since we are given a 95% level of confidence, the critical values for the Chi-square distribution with degrees of freedom (df) equal to n-1 (n=17) and a significance level of 0.05/2 (two-tailed test) are 7.261 and 28.412, respectively.

Using the formula (n-1)s^2/χ^2(df,α/2) and (n-1)s^2/χ^2(df,1-α/2), where s^2 is the sample variance and α is the significance level, we can calculate the lower and upper bounds of the confidence interval. Substituting the given values, we get:

Lower bound: (17-1)×(98.5294)/28.412 = 54.9471
Upper bound: (17-1)×(98.5294)/7.261 = 1274.1194

Therefore, the 95% confidence interval for the population variance is (54.95, 1274.12) ounces^2. This means that we are 95% confident that the true variance of the population lies within this interval.

It is important to note that this interval does not contain any negative values, which is expected for a variance measure. Also, since the sample is assumed to be from a normally distributed population, this assumption should be checked using appropriate tests or techniques.

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Find X both segments are tangents

Answers

Answer:

c

Step-by-step explanation:

Answer:

D

Step-by-step explanation:

2x+10=x+30

so, the answer is 30.

Leaking gas tanks. Leakage from underground gasoline tanks at service stations can damage the environment. It is estimated that 25% of these tanks leak. You examine 15 tanks chosen at random, independently of each other. (a) What is the mean number of leaking tanks in such samples of 15? (b) What is the probability that 10 or more of the 15 tanks leak? (c) Now you do a larger study, examining a random sample of 2000 tanks nationally. What is the probability that at least 540 of these tanks are leaking?

Answers

(a) The mean number of leaking tanks is 3.75. (b) The probability that 10 or more of the 15 tanks leak is 0.114 or 11.4%. (c) The probability that at least 540 of these tanks are leaking is 3.22%

(a) The mean number of leaking tanks in such samples of 15 can be calculated using the formula for the mean of a binomial distribution, which is mean = np, where n is the sample size and p is the probability of success. In this case, n = 15 and p = 0.25 (since 25% of tanks leak), so the mean number of leaking tanks is 15 x 0.25 = 3.75.

(b) To calculate the probability that 10 or more of the 15 tanks leak, we can use the binomial distribution again. The formula for this probability is P(X ≥ 10) = 1 - P(X ≤ 9), where X is the number of leaking tanks. Using a binomial calculator or a probability distribution table, we can find that P(X ≤ 9) = 0.886 and therefore P(X ≥ 10) = 1 - 0.886 = 0.114 or 11.4%.

(c) To calculate the probability that at least 540 of the 2000 tanks are leaking, we can use the normal approximation to the binomial distribution, since the sample size is large and the probability of success is not too small or too large (0.25 in this case). We first calculate the mean and standard deviation of the number of leaking tanks: mean = np = 2000 x 0.25 = 500 and standard deviation = sqrt(np(1-p)) = sqrt(2000 x 0.25 x 0.75) = 21.65 (rounded to two decimal places). Then, we standardize the value 540 using the formula z = (x - mean) / standard deviation, where x is the number of leaking tanks we want to find the probability for. Thus, z = (540 - 500) / 21.65 = 1.85 (rounded to two decimal places). Using a normal distribution table or calculator, we can find that the probability of getting a z-score of 1.85 or higher is 0.0322 or 3.22%. Therefore, the probability that at least 540 of the 2000 tanks are leaking is 3.22%.

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The power for a one-sided test of the null hypothesis = 10 versus the alternative = 8 is equal to 0.8. Assume the sample size is 25 and = 4. What is , the probability of a Type I error?

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The probability of a Type I error is 0.2 or 20%. This means that there is a 20% chance of rejecting the null hypothesis when it is actually true.

The power of a hypothesis test is the probability of rejecting the null hypothesis when the alternative hypothesis is true. In this case, the power of the test is given as 0.8, and the null hypothesis is that the true value of the parameter is 10, while the alternative hypothesis is that the true value is 8.

We are given the sample size, n = 25, and the standard deviation, σ = 4. To calculate the probability of a Type I error, we need to determine the significance level of the test, denoted by α.

The significance level is the probability of rejecting the null hypothesis when it is actually true. It is usually set before conducting the test, and commonly set at 0.05 or 0.01.

To calculate α, we can use the following formula:

α = 1 - power = 1 - 0.8 = 0.2

So, the probability of a Type I error is 0.2 or 20%. This means that there is a 20% chance of rejecting the null hypothesis when it is actually true.

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A rectangular frame needs to have an opening of 27 square inches. The boards used to create the frame have a width of 1 1/2 inches. What should be the dimensions of the frame so that the least amount of framing is used

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To minimize the use of framing, the rectangular frame should have dimensions of around 9.3 inches by 2.9 inches.

What are the dimensions of a rectangular frame with an opening of 27 square inches, if the boards used to create the frame have a width of 1 1/2 inches and the least amount of framing is to be used?

Let's assume the length and width of the rectangular frame be L and W, respectively. The total area of the frame can be expressed as:

Total Area = (L + 3W) * (W + 3L) [adding 1.5 inch of framing to each side]

The opening of the frame is given as 27 square inches:

L * W = 27

We can substitute the value of L from the second equation into the first equation and simplify:

Total Area = (27/W + 3W) * (W + 3*27/W)Total Area = (27/W + 3W) * (W + 81/W)

Expanding the brackets and simplifying:

Total Area = 3W² + 27*3 + 81/W + 27/W²

We can now take the derivative of this expression with respect to W and set it to zero to find the value of W that minimizes the total area:

d(Total Area)/dW = 6W - 81/W² = 06W = 81/W²W³ = 13.5W = (13.5)⁽¹/³⁾W ≈ 2.9 inches

Substituting the value of W back into the equation L * W = 27:

L = 27/WL ≈ 9.3 inches

Therefore, the dimensions of the frame should be approximately 9.3 inches by 2.9 inches to minimize the amount of framing used.

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a. Use .10 to test for a statistically significantly difference between the population means for first- and fourth-round scores. What is the -value

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To test for a statistically significant difference between the population means for first- and fourth-round scores, we can use a two-sample t-test with a significance level of .10.

Assuming that the sample data meets the necessary assumptions for a t-test (e.g. normality, equal variances), we can calculate the t-statistic using the following formula:

t = (x1 - x4) / (s√(1/n1 + 1/n4))

where x1 and x4 are the sample means for first- and fourth-round scores, s is the pooled standard deviation, n1 and n4 are the sample sizes for the two groups.

Once we have calculated the t-statistic, we can determine the corresponding p-value using a t-distribution table or calculator. The p-value represents the probability of obtaining a t-statistic as extreme or more extreme than the one observed, assuming the null hypothesis (i.e. no difference between the population means) is true.

If the p-value is less than .10, we can reject the null hypothesis and conclude that there is a statistically significant difference between the population means. On the other hand, if the p-value is greater than .10, we fail to reject the null hypothesis and conclude that there is not enough evidence to suggest a difference between the population means.

Therefore, to answer the question, we need to know the sample means, standard deviations, and sample sizes for the first- and fourth-round scores, and use them to calculate the t-statistic and p-value. Without this information, we cannot determine the exact value of the p-value.

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If the ball leaves the bat at 90 mph , how much time elapses between the hit and the ball reaching the pitcher

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It would take approximately 0.458 seconds for the ball to travel from the hitter to the pitcher, assuming no other factors affecting the ball's trajectory.

To calculate the time elapsed between the hit and the ball reaching the pitcher, we need to know the distance between the hitter and the pitcher, as well as the speed of the ball.

Let's assume that the distance between the hitter and the pitcher is 60.5 feet, which is the distance between the pitcher's mound and home plate in baseball.

Assuming that there is no air resistance or other factors affecting the ball's trajectory, we can use the following equation to calculate the time elapsed:

time = distance / speed

In this case, the speed of the ball is 90 mph, which is equivalent to 132 feet per second. So:

time = 60.5 feet / 132 feet per second

time = 0.458 seconds

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Use the sum of the first 10 terms to approximate the sum S of the series. (Round your answers to five decimal places.1/ sqrt(n^8 + 3) from n=1 to the sum of infinity

S approximately equals..???

Estimate the error.

error is less than or equal to...???

Answers

The sum S of the series is approximately 0.86832, and the error is less than or equal to 0.01295.

Using the sum of the first 10 terms, we can approximate the sum S of the series as follows:

S ≈ sum of first 10 terms
  ≈ 0.86832

To estimate the error, we can use the remainder formula for an infinite series:

Rn = Sn - S
  = sum from n+1 to infinity of 1/sqrt(n^8 + 3)

Since we are trying to estimate the error using the sum of the first 10 terms, we can use n = 10 in the remainder formula:

R10 = sum from 11 to infinity of 1/sqrt(n^8 + 3)

To find an upper bound for R10, we can use the integral test:

1/sqrt(x^8 + 3) is a decreasing function for x ≥ 1, so we can use the integral from 10 to infinity to find an upper bound for R10:

integral from 10 to infinity of 1/sqrt(x^8 + 3) dx
≈ 0.01295

Therefore, we can estimate the error as:

error ≤ R10
     ≤ 0.01295

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2. For each system of equations indicate whether or not the equation has no real solution, one real solution, or Infinite solutions.
A, 5(11x + 4) - x = 61x + 20
B, 7(5x + 10) - x = 34x + 74
C. 6x + 8 + x = 7x + 6
D. 5(x − 12) + 3x = 8x = 60

Answers

Three of the system of equations has no solution and one have Infinite solutions.

Given are system of equations, we need to solve them,

A) 5(11x + 4) - x = 61x + 20

55x+20-x = 61x+20

55x = 62x [no solution]

B) 7(5x + 10) - x = 34x + 74

35x + 70 - x = 34x+74

34x + 70 = 34x + 74

70 = 74 [no solution]

C) 6x + 8 + x = 7x + 6

7x + 8 = 7x +6 [no solution]

D) 5(x − 12) + 3x = 8x - 60

5x-60+3x = 8x-60

8x-60 = 8x-60 [Infinite solutions]

Hence, three of the system of equations has no solution and one have Infinite solutions.

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