Noise levels at 7 manufacturing plants were measured in decibels yielding the following data:

Noise levels at manufacturing plants were measured in decibels yielding the following data:

Construct the confidence interval for the mean noise level at such locations. Assume the population is approximately normal.

Step 3 of 4 :  Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places.

Step 4 of 4