Question

A quality inspector took five samples, each with four observations (n = 4), of the length of
time for glue to dry. The analyst computed the mean of each sample and then computed the grand
mean. All values are in minutes. Use this information to obtain three-sigma (i.e., z = 3) control
limits for means of future times. It is known from previous experience that the standard deviation
of the process is .02 minute.

Answer 1

Answer:

Grand mean = X

Standard deviation = SD

X = (12.10+12.12+12.11+12.10+12.12) / 5

X = 12.11

SD = 0.02 / (4)1/2

SD = 0.01