In an experiment to determine the effect of curing time on the compressive strength of a certain type of concrete, the mean strengths, in MPa, for specimens cured for each of four curing times were X̅₁. = 1316, X̅_2. = 1326, X̅_3. = 1375, and X̅_4. = 1389. Assume that four specimens were cured for each curing time.

a. If MSE = 875.2, compute the value of the F statistic for testing the null hypothesis that all four curing times have the same mean strength. Can this null hypothesis be rejected at the 5% level?

b. Use the Tukey–Kramer method to determine which pairs of curing times, if any, may be concluded to differ at the 5% level.