Question 1

If the standard deviation is increased and the sample size and confidence level stay the same, then the margin of error will also be increased.

• True
• False

Question 2

If we have already decided on the Error and confidence level for a confidence interval, then a population with a standard deviation of 30 will require a greater sample size than a population with a standard deviation of 20.

• True
• False

Question 3

A 95% confidence interval for the mean was computed with a sample of size 90 to be (16,22). Then the Error 3.

• True
• False

Question 4

If a 95% confidence interval for the mean was computed as (25,50), then if several more samples were taken with the same sample size, then 95% of them would have a sample mean between 25 and 50.

• True
• False

Question 5

If n = 16,xx= 34, and s = 15, construct a confidence interval at a 98% confidence level. Assume the data came from a normally distributed population. Give your answers to three decimal places. <<

Question 6

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 78.4 for a sample of size 22 and standard deviation 10.2. Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 95% confidence level).Assume the data is from a normally distributed population.

Enter your answer as a tri-linear inequality accurate to three decimal places. <<

Question 7

A researcher is interested in finding a 90% confidence interval for the mean number of times per day that college students text. The study included 107 students who averaged 31.2 texts per day. The standard deviation was 19.5 texts.

a. To compute the confidence interval use a ? t z distribution.

b. With90% confidence the population mean number of texts per day is between and texts.

c.If many groups of 107 randomly selected members are studied, then a different confidence interval would be produced from each group. About percent of these confidence intervals will contain the true population number of texts per day and about percent will not contain the true population mean number of texts per day.

Question 8

A researcher is interested in finding a 98% confidence interval for the mean number minutes students are concentrating on their professor during a one hour statistics lecture. The study included 150 students who averaged 39.4 minutes concentrating on their professor during the hour lecture. The standard deviation was 13.4 minutes.Round answers to 3 decimal places where possible.

a. To compute the confidence interval use a ? z t distribution.

b. With98% confidence the population mean minutes of concentration is between and minutes.

c.If many groups of 150 randomly selected members are studied, then a different confidence interval would be produced from each group. About percent of these confidence intervals will contain the true population mean minutes of concentration and about percent will not contain the true population mean minutes of concentration.

Question 9

You are interested in finding a 98% confidence interval for the mean number of visits for physical therapy patients. The data below show the number of visits for 15 randomly selected physical therapy patients. Round answers to 3 decimal places where possible.

15

20

9

13

21

5

18

7

8

24

10

17

28

15

7

a. To compute the confidence interval use a ? t z distribution.

b. With98% confidence the population mean number of visits per physical therapy patient is between and visits.

c.If many groups of 15 randomly selected physical therapy patients are studied, then a different confidence interval would be produced from each group. About percent of these confidence intervals will contain the true population mean number of visits per patient and about percent will not contain the true population mean number of visits per patient.

Question 10

You are interested in finding a 95% confidence interval for the average commute that non-residential students have to their college. The data below show the number of commute miles for 12 randomly selected non-residential college students.

21

7

7

17

23

16

25

5

24

17

6

14

a. To compute the confidence interval use a ? t z distribution.

b. With95% confidence the population mean commute for non-residential college students is between and miles.

c.If many groups of 12 randomly selected non-residential college students are surveyed, then a different confidence interval would be produced from each group. About percent of these confidence intervals will contain the true population mean number of commute miles and about percent will not contain the true population mean number of commute miles.

Question 11

You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately=35.6=35.6. You would like to be 95% confident that your estimate is within 2 of the true population mean. How large of a sample size is required? n=