1. A sample size of n = 71 is drawn from a population whose standard deviation is known to be ? = 4.8. Find the critical value for a 99% confidence interval for ?.

2.58

1.96

1.88

2.65

2. Why do we use inferential statistics?

To help explain the outcomes of random phenomena

To make informed predictions about population parameters we don't know

To describe samples that are normal and large enough (n > 30)

To generate samples of random data for a more reliable analysis

Question 3

Which of the following variables corresponds to margin of error?

s

n

E

Question 4

A survey of 500 shoppers found that 17% of them shop on impulse. Assuming a 99% confidence level, find the margin of error.

0.01

0.04

0.17

0.09

Question 5

Find the critical value for a 92% confidence level when finding the sample size for a population proportion.

1.645

1.96

1.75

2.0

Question 6

A music producer would like to estimate the mean length of all songs published after 1980. How many songs should be in the sample if we want 90% confidence that the sample mean is within 20 seconds of the population mean? Note that a previous sample showed a standard deviation of 60 seconds.

25 songs

24 songs

55 songs

56 songs

1. Question 7

A sample of 20 cupcakes found that the average calories were 250 with a standard deviation of 50 calories. What is the 95% confidence interval for the mean calorie value of all cupcakes?

209.39 < ? < 290.61

226.60 < ? < 273.40

193.17 < ? < 306.83

237.90 < ? < 262.10

1. Question 8

Which of the following confidence levels gives the lowest probability that the confidence interval contains the population parameter?

0.90

0.95

0.98

0.99

1. Question 9

Changing which of the following values would NOT change the sample size needed when estimating a confidence interval?

Margin of error

Critical value

Sample statistic

Standard deviation

1. Question 10

An epidemiologist plans to conduct a survey to estimate the percentage of pregnant women who give birth before their due dates. How many women must be surveyed in order to be 99% confident that the estimated percentage is in error by no more than two percentage points? Assume that a prior study showed that 73% of women give birth before their due date.

3280 pregnant women

3279 pregnant women

2540 pregnant women

2539 pregnant women

1. Question 11

What is the value of alpha if the confidence level is 98%?

0.02

0.20

0.98

0.08

1. Question 12

Decreasing the confidence level while holding the sample size the same, will do what to the length of your confidence interval?

Make it bigger

Make it smaller

Keep it the same

Unable to be determined from the given information.

1. Question 13

In a survey of 600 voters, it was found that 222 of them had voted "no" for a new city measure. Calculate a 95% confidence interval for p.

0.3314 < p < 0.4086

0.3112 < p < 0.4288

0.3502 < p < 0.3898

0.2678 < p < 0.4722

1. Question 14

A random sample of 65 dogs found that 23 of them preferred a yellow ball to a red ball. What is the p-hat for this sample?

0.123

0.354

0.650

0.283

1. Question 15

A sample of 50 batteries had a mean lifetime of 120.1 hours with a standard deviation of 20 hours. What is the margin of error with a 90% confidence level?

4.65 hours

5.91 hours

7.88 hours

4.74 hours