Confidence Interval Margin of Error

A company is reaching out to customers who bought a pedometer watch. It wants to construct a 90% confidence interval for the mean rating of its pedometer watch. If the company wants S=1.2 and MoE of 0.2. How many people should they contact to obtain this margin of error? (Round to a whole number).

A 90% confidence interval for the average salary of all CEOs in the electronics industry was constructed using the results of a random survey of n CEOs. It was found that the standard deviation was $1,000 and the margin of error was $300. How many CEOs was included in the survey? (Round to the nearest whole number)

In a crash test of 15 troopers, collision repair costs are found to have a distribution that is approximately normal, with a mean of $1800 and a sample standard deviation of $950. Construct a 99% confidence interval for the repair cost. 

• (1069.77, 2530.23)

• (1077.13, 2522.87)

• (1167.15, 2432.85)

• None of these.

If the margin of error in a confidence interval is 4, what is the range of the confidence interval around a sample mean of 50?

• 46 to 54

• 48 to 52

• 45 to 55

• 49 to 51

A confidence interval for the mean score of a test is (75, 85). What is the margin of error?

• 5

• 10

• 15

• 20

If the sample mean is 100 and the margin of error is 5, what is the upper bound of the 95% confidence interval?

• 95

• 105

• 100

• 110

What effect does doubling the sample size have on the margin of error in a confidence interval, assuming the confidence level remains constant?

• The margin of error is cut in half.

• The margin of error remains the same.

• The margin of error doubles.

• The margin of error is reduced, but not cut in half.

If you increase the confidence level from 90% to 95%, what happens to the margin of error?

• It decreases.

• It stays the same.

• It increases.

• It becomes zero.

How does decreasing the sample size from 150 to 100 affect the margin of error in a confidence interval, assuming all else remains constant?

• The margin of error decreases.

• The margin of error increases.

• The margin of error stays the same.

• The margin of error becomes zero.

For a given confidence level, if the margin of error is 3 and the sample mean is 50, what is the lower bound of the confidence interval?

• 47

• 53

• 50

• 49