The time needed for performing a machining operation is to be investigated. Historically, the process has had a standard deviation equal to 0.152 minutes. The means (in minutes) of 39 samples of n = 6 are: Sample Mean Sample Mean Sample Mean 1 3.75 14 3.89 27 3.90 2 3.91 15 3.89 28 3.77 3 3.93 16 3.68 29 3.83 4 3.84 17 3.85 30 3.82 5 3.82 18 3.78 31 3.89 6 3.96 19 3.72 32 3.82