What changes would decrease the margin of error?

Question

Which of the following changes would decrease the margin of error? (Choose all that apply; there may be more than one answer)

A. The sample mean increases

B. The standard deviation increases

C. The level of confidence increases

D. The sample size increases

Answer 1

The formula for the margin of error is:

 

Zvalue corresponding the level of Confidence Required * Standard Deviation ÷ √Sample size

 

A. The sample mean increases - will have no effect

B. The standard deviation increases - this will increase the margin of error

C. The level of confidence increases - as the level of confidence increases, the Z value increases which increases the margin of error

 

The only answer is D

 

D. The sample size increases - since the sample size is in the denominator of the margin of error calculation, increasing the sample size decreases the margin of error.