The mean length of a candy bar is 43 millimeters. there is concern that the settings of the machine cutting the bars have changed. test the claim at the 0.02 level that there has been no change in the mean length. the alternate hypothesis is that there has been a change. twelve bars (n = 12) were selected at random and their lengths recorded. the lengths are (in millimeters) 42, 39, 42, 45, 43, 40, 39, 41, 40, 42, 43, and 42. the mean of the sample is 41.5 and the standard deviation is 1.784. computed t = -2.913. has there been a statistically significant change in the mean length of the bars?