Minimum Sample Size

The standard IQ test has a mean of 100 and a standard deviation of 15. We want to be 95% certain that we are within 3 IQ points of the true mean. Determine the required sample size.

• 97

• 334

• 250

• 20

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

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

You wish to estimate, with 90% confidence, the population proportion of adults who read fiction books. Your estimate must be accurate to within 2% of the population proportion. A prior study found that 47% of adults read fiction books. What is the minimum required sample size? Round up your answer to the nearest whole number.

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

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? ANSWER THIS QUESTION: What critical z-score value should be used?

• 1.645

• 1.96

• 2.575

• 2.8

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

You wish to estimate, with 90% confidence, the population proportion of adults who read fiction books. Your estimate must be accurate to within 2% of the population proportion. A prior study found that 47% of adults read fiction books. What is the proportion of failures in decimal form (Refer to the figure)?

A quality control manager wants to estimate the proportion of defective items produced by a machine with a margin of error of 0.02 and a 95% confidence level. If historical data suggest that the proportion of defective items is around 0.1, how many items should be sampled?

• 864

• 865

• 608

• 609

A researcher wants to estimate the average height of students in a university with a margin of error of 0.05 meters and a 90% confidence level. If the population standard deviation is known to be 0.2 meters, what sample size is required?

• 26

• 27

• 44

• 43