QUESTION 6. Spacer collars are manufactured by a machine which should produce a mean thickness of $39 \mathrm{-mm} $ : too thick or thin means that the collars are not useable. A sample of six collars is collected and the data is (in millimeters): $39.030,38.997,39.012,39.008,39.019,39.002$ Test the hypothesis that the machine is producing collars to specification at the $1 %$ level. SP.VS.790