As can be seen from the analysis of variance summary table shown below, MSE = 21.722.

Source df Ssq Ms F p Groups 4 274.913 68.728 3.16 .039 Error 18 391.000 21.722 Total 22 665.913 30.269

= (1)²/5 + (1)²/4 + (-1)²/5 + (-1)²/5 + (0)²/4 = .85

Therefore,

= 4.297. (Click here for formula for s

Finally,

= 10.3/4.297 = 2.397.

The degrees of freedom error = N-a = 23 - 5 =18 (see the summary table). From a t table it can be determined that the probability value associate with a t of 2.397 with 18 df is 0.028.