When constructing a confidence interval, as the confidence level required in estimating the mean increases, the width of the confidence interval . remains the sameb. increasesc. decreases

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:

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

$54.99

step-by-step explanation:

$54.99 includes 500 min. if she does not exceed 500 min then her bill is $54.99

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