Question

The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 6.0 minutes. It is known that the standard deviation of the checkout time is 2.0 minutes. Refer to Exhibit 8-2. If the confidence coefficient is reduced to 0.90, the margin of error becomes negative will increase will decrease remains unchanged

Answer 1

Margin of error is directly proportional to the z-value corresponding to the confidence coefficient.

Now, z-value decreases when the confidence coefficient is reduced.

Thus, the margin of error will decrease

The corresponding margin of error will be

$z_{\frac{.90}{2}}*\frac{\sigma}{\sqrt{n}}$

= $1.645*\frac{2}{\sqrt{100}}$

= 0.329