Question

A quality inspector took five samples, each with 4 observations, of the length of time for glue to dry. The analyst computed the mean of each sample, and then computed the grand mean of 12.14. Use this information to obtain the three-sigma upper control limit for the means of future times. It is known from previous experience that the standard deviation of the process is 0.05.

Answer 1

12.57

Step-by-step explanation:

The first part is correct with the answer of 12.57. The formula is x_bar_bar + 3*sigma/sqrt(n)

Here x_bar_bar = 12.51, sigma = 0.04, n = 4.

Thus UCL = 12.51 + 3*0.04/sqrt(4) = 12.57