Chapters 18-19 Summative Assessment

Question

Ms. Timlin calculated a 95% confidence interval. She doesn't want to lose any confidence, but she wants to have a smaller margin of error. Which of the following can she do to achieve this? 

I.  change the z* value to a smaller number.

II. take a larger sample.

III. take a smaller sample.

 

a	II only
b	I and III
c	I only
d	I and II
e	III only

Answer 1

The z* value is fixed for the desired confidence level, so if you change that, you change the confidence level, so I is not an option.

If you take a larger sample the margin of error will be reduced because the standard error portion of the margin of error computation has the square root of n in the denominator.. So II is an option.

Conversely, taking a smaller sample size, will increase the standard error potion of the margin of error computation and increase the margin of error, so III is not an option.

Final answer is a - II only.