Question

A consumer affairs investigator records the repair cost for 4 randomly selected washers. A sample mean of $64.26 and standard deviation of $27.77 are subsequently computed. Determine the 80% confidence interval for the mean repair cost for the washers. Assume the population is approximately normal. Step 1 of 2 : Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places.

Answer 1

The critical value that should be used in constructing the confidence interval is approximately 1.28.

Step-by-step explanation:

To find the critical value for a confidence interval, we need to look up the Z value corresponding to the desired confidence level. In this case, the confidence level is 80%, which means we need to find the Z value for a 90% confidence level (since the remaining 10% is split equally in the tails of the distribution).

Using a Z-table or a statistical software, we can find that the Z value for a 90% confidence level is approximately 1.28. Therefore, the critical value to be used in constructing the confidence interval is 1.28.