Confidence Interval Margin of Error

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)

(a)  

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. 

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?

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

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

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

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

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

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?