More about Confidence Intervals

Question 1

A 90% confidence interval for the mean time it takes to run 1 mile for all high school track athletes is computed from a simple random sample of 200 track athletes and is found to be 6.2 ± 0.8 minutes. We may conclude that:

Revolt · Accepted Answer

if we took many, many random samples of the same size and computed their confidence intervals, approximately 90% of the intervals will capture the true mean running time.

Question 2

172329✔ 95

Revolt · Accepted Answer

95

Question 3

✔ true proportion of adults whoproportion of adults who said theysample of those who report they

Revolt · Accepted Answer

true proportion of adults who

Question 4

⇒ 300

Revolt · Accepted Answer

170798

Question 5

After interviewing 1,200 people, a Gallup Poll reports with 95% confidence that 23% of adults exercise at least 3 times a week with a margin of error of 6%.

Revolt · Accepted Answer

If we were to select many random samples of from the same population and construct a 95% confidence interval using each sample, about % of the intervals would capture the exercise.: 1,200 people; If we were to select many random samples of from the same population and construct a 95% confidence interval using each sample, about % of the intervals would capture the exercise.: 95; If we were to select many random samples of from the same population and construct a 95% confidence interval using each sample, about % of the intervals would capture the exercise.: true proportion of adults who

Question 6

After interviewing 1,200 people, a Gallup Poll reports with 95% confidence that 23% of adults exercise at least 3 times a week with a margin of error of 6%. Interpret the confidence level in the context of the scenario. If we were to select many random samples of from the same population and construct a 95% confidence interval using each sample, about % of the intervals would capture the exercise.

Revolt · Accepted Answer

1,200 people; Selection 1: 1,200 people; Selection 2: 95; Selection 3: true proportion of adults who

Question 7

The state government claims that the average earnings for a high school student who works during the summer is $1,500. A survey of 200 local high school students determined that the average amount of money earned at a summer job in the area was $1,100 and a 90% confidence interval was found to be ($975, $1,225). The confidence level is interpreted to mean that:

Revolt · Accepted Answer

if we repeat our survey many times, then about 90% of our confidence intervals will contain the true amount earned at a summer job.

Question 8

One hundred tomato plants were randomly selected from a large garden, and a 90% confidence interval was computed to determine the true proportion of plants that produce useable tomatoes. The interval is 0.86 to 0.92.What would happen to the width of the confidence interval if the sample size was quadrupled?

Revolt · Accepted Answer

The interval would be half the original width.

Question 9

One hundred tomato plants were randomly selected from a large garden, and a 90% confidence interval was computed to determine the true proportion of plants that produce useable tomatoes. The interval is 0.86 to 0.92.What would happen to the width of the confidence interval if the confidence level increased to 95%?

Revolt · Accepted Answer

The width of the interval would increase.

Question 10

What can be done to decrease the margin of error? Check all that apply.

Revolt · Accepted Answer

Increase the sample size.; Decrease the confidence level.

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