Question

After constructing a confidence interval estimate for a population mean, you believe that the interval is useless because it is too wide. In order to correct this problem, you need to: a. increase the sample size b. increase the sample mean c. increase the confidence coefficient d. decrease the sample size e. increase the population size

Answer 1

a. increase the sample size

Explanation:

The width of a confidence interval is twice the margin of error, which is given by:

`M = z*(\sigma)/(√(n))`

In which
`\sigma` is the standrd deviation of the population, n is the size of the sample, and z is the confidence coefficient(the higher the confidence level, the higher z is).

The only of those variables which is direct proportional to M is the sample size. This means that if we want to decrease the width of M, we need to increase the sample size.

So the correct answer is:

a. increase the sample size