Answer:
b. increases
Step-by-step explanation:
The width of a confidence interval of x%, that is, the margin of error of the interval, is given by:
[tex]M = z*\frac{\sigma}{\sqrt{n}}[/tex]
In which z is dependent on the confidence interval, and related to the z table. A higher confidence level means a higher pvalue in the z table, so a higher value of z.
The width M and z are direct proportional. That is, as z increases, so does M.
So the correct answer is:
b. increases
