The mean length of the small counter balance bar is 43 millimeters. There's concern that the adjustments of machine producing the bars have changed. Test the claim at 0.02 level that there has been no change in mean length. The alternate hypothesis is that there has been the change. Twelve bars (n = 12) were chosen 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 sample is 41.5 and standard deviation 1.784. Computed t = - 2.913. Has there been the statistically significant change in mean length of the bars?

a. Yes, because the evaluated t lies in the area beyond critical.  

b. No, because the information given isn't complete.

c. No, because the computed t lies in area to the right of -2.913.

d. None of above