Sample Size Margin of Error

For a class project, a student in a statistics class surveys the monthly rent for 32 unfurnished one-bedroom apartments in Boston and finds the mean monthly rent to be $1400 with a standard deviation of $220. Find the margin of error for the sample mean. (assuming 95% confidence) Round to the nearest hundredth

• $77.78

• $4.31

• $188.78

• $494.97

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

A researcher wishes to estimate, within $25, the true mean amount of postage a community college spends each year. The standard deviation is known to be $80. If she wishes to be 95% confident in her estimate of the true mean amount of postage, how large a sample is necessary? Round to the nearest whole number

• 41

• 25

• 80

• 200

Suppose a department store wants to estimate within 2 years the true mean age of the customers in its contemporary apparel department. The department store manager assumes a standard deviation of 7.5 years. How large a sample is required to estimate the true mean age with 95% confidence?

Round to the nearest whole number

• 56

• 112

• 420

• 224

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

• B

• C

• D

Determine whether the action would increase or decrease the margin of error:

Increase the sample size

• Margin of error increases

• Margin of error decreases

If the mean of a sample is 203 and the margin of error is 4.6, what would be a reasonable mean for the population?

• 99.2

• 198.3

• 207.2

• 207.7

Researchers want to estimate with 95% confidence the true mean pulse rate of American adult males who jog at least 15 miles per week. They survey 21 males and find the sample mean pulse rate to be 52.6 beats per minute and a standard deviation of 3.22 beats per minute. Find the margin of error for the mean pulse rate of all American adult males who jog at least 15 miles per week. Round to the nearest tenth.

• 1.4 beats per minute

• 1.7 beats per minute

• 0.9 beats per minute

• 4.1 beats per minute