An Economics teacher started class one day by drawing the names of students out of a hat and asked them to do as many pushups as they could. The n = 14 randomly selected students averaged 16 pushups per person (sample mean) with a standard deviation of 8 pushups (sample standard deviation). Suppose the distribution of the population of number of pushups that can be done is approximately normal.

What is the standard error of the mean?

0.900

2.138

2.876

3.061

4.743

Question 2 Using the built-in Excel function T.INV.2T, find the t critical value for 99% confidence interval estimation based upon a sample of size n = 15. The correct t value is

1.645.

1.812.

2.576.

2.977

3.169.

Question 3 A statistics teacher started class one day by drawing the names of n = 16 students out of a hat and asked them to do as many pushups as they could. The 16 randomly selected students averaged 15.2 pushups per person with a standard deviation of 8.5 pushups. Suppose the distribution of the population of number of pushups that can be done is approximately normal.

The 95% confidence interval for the true mean number of pushups that can be done is

5.85 to 24.15.

8.56 to 21.44.

10.67 to 19.73.

11.31 to 18.55.

13.15 to 16.83.

Question 4 George Smith own's George's Joint, a gas station and convenience store. George is trying to get a better understanding of his business and wants to estimate the mean number of gallons of gasoline sold to his customers. Assume the number of gallons of gasoline sold follows a normal distribution with a population standard deviation of 2.3 gallons. From his records, he randomly selects 60 sales and find the mean number of gallons sold is 8.6.

What is the point estimate of the population mean?

60

2.3

8.6

17

43

Question 5 A national company with several locations in the DFW area wants to provide on-site childcare for their employees. As part of a feasibility study, they wish to estimate the mean weekly childcare cost for their employees that have young children in full-time childcare facilities. The attached file contains the amounts spent for childcare in a week by 10 randomly selected employees.

Homework 3 - 1.xlsx

Develop a 90% confidence interval.

What is the lower boundary for the 90% confidence interval for the mean?

Your answer should be in the form of xx.xx

Question 6 University System of Texas wants to estimate the proportion of students who will need 24-hours library access all year long. Suppose a sample of 500 student was taken. If 120 need 24-hours library access, calculate a 90% confidence interval for the population proportion.

[0.2135, 0.2523]

[0.2086, 0.2714]

[0.1145, 0.1723]

[0.2734, 0.3715]

Question 7 A random sample ofn= 225 elements is selected from a target population. The sample mean is 180 and the standard deviation is 75. An approximate 95% confidence interval for the mean is

175 to 185

170 to 190

105 to 125

145 to 167

Question 8 A newly hired City of Dallas Data Scientist is interested in studying the incomes of Denton county residents. The population standard deviation is known to be $2,000. A random sample of 100 individuals resulted in a mean income of $35,000. What is the width of the 90% confidence interval? (Hint: get the margin of error (MOE) first The width is measured as 2*MOE)

$328.971

$657.941

$1.644

$200

$567.987

Another set

The purpose of statistical inference is to make estimates or draw conclusions about a

sample based upon information obtained from the population.

population based upon information obtained from the sample.

statistic based upon information obtained from the population.

mean of the sample based upon the mean of the population.

Question 2

The basis for using a normal probability distribution to approximate the sampling distributions of sample means and sample proportions is

Chebyshev's theorem.

the empirical rule.

the central limit theorem.

Bayes' theorem.

Question 3

When the expected value of the point estimator is equal to the population parameter it estimates, it is said to be

unbiased.

precise.

symmetric.

predicted.

Question 4

An estimate of a population parameter that provides an interval of values believed to contain the value of the parameter is known as the

confidence level

confidence interval

parameter value

point estimate

Question 5

The value added and subtracted from a point estimate in order to develop a confidence interval estimate of the population parameter is known as the

confidence level

interval estimate

margin of error

point estimate

Question 6

Parameters are

numerical characteristics of a sample.

numerical characteristics of a population.

the averages taken from a sample.

numerical characteristics of either a sample or a population

Question 7

A population characteristic, such as a population mean, is called

a statistic

a parameter

a sample

the mean deviation

Question 8

As the sample size increases, the

standard deviation of the population decreases

population mean increases

standard error of the mean decreases

standard error of the mean increases

Question 9

Sampling a population is often necessary because the cost of studying all the items in the population is prohibitive.

TRUE

FALSE

Question 10

The t distribution approaches the standardized normal distribution when the number of degrees of freedom increases.

TRUE

FALSE