Minimum Sample Size Margin of Error

A cheese processing company wants to estimate the mean cholesterol content of all one-ounce servings of cheese. The estimate must be within 0.5 milligram of the population mean. Assume that the population standard deviation is 2.8 milligrams. What is the minimum required sample size to construct a 90% confidence interval for the population mean? Round up your answer to the nearest whole number.

• 85

• 84

• 120

• 121

REFER TO THIS PROBLEM:   A cheese processing company wants to estimate the mean cholesterol content of all one-ounce servings of cheese. The estimate must be within 0.5 milligram of the population mean. Assume that the population standard deviation is 2.8 milligrams. What is the minimum required sample size to construct a 90% confidence interval for the population mean? What critical z-score value should be used?

• 1.645

• 1.96

• 2.575

• 2.8

You will be conducting a study to estimate the average daily food expenditure of students. You want to be 95% confident that the sample mean will be within Php20 of the true mean. If you approximate the population standard deviation to be Php100 and assume an approximately normal distribution, what is the minimum sample size that you should get? Round up your answer to the nearest whole number.

• 96

• 97

• 67

• 68

You wish to estimate, with 99% confidence, the population proportion of employees who prefer a four-day work week. Your estimate must be accurate to within 4% of the population proportion. If no preliminary estimate is available, then what value should be used for the proportion of successes (Refer to the figure)?

• 0.5

• 0.01

• 0.04

• 0.99

• A

• B

• C

• D

What can you do to reduce the margin of error? 

• increase sample size

• decrease sample size

How could Javier decrease the margin of error?

• Increase the sample size

• Decrease the sample size

A sample of n students were asked for the average amount of money they spend in a day. The data resulted in a mean of $5.50 with a standard deviation of $2.45. If the margin of error was $0.31, how many students were in the sample? Round to the nearest whole student

• 250

• 16

• 100

• 500

You wish to estimate, with 99% confidence, the population proportion of employees who prefer a four-day work week. Your estimate must be accurate to within 4% of the population proportion. What is the margin of error (in decimal form)?

You wish to estimate, with 99% confidence, the population proportion of employees who prefer a four-day work week. Your estimate must be accurate to within 4% of the population proportion. What is the minimum required sample size if no preliminary estimate is available? Round up your answer to the nearest whole number.

• 1,036

• 1,037

• 422

• 423