12.50 A randomized block design has five different age groups as blocks, and members of each block have been randomly assigned to the treatment groups shown here.

For these data, use the 0.05 level in determining whether the treatment effects could all be zero. Using the 0.01 level, evaluate the effectiveness of the blocking variable.

(Use data file XR12050.)

Treatment 1 2 3 4 A 51.2 50.3 47.2 42.0 B 41.0 37.6 37.0 35.7 Block C 57.5 56.9 54.7 49.2 D 51.2 49.3 46.9 50.9 E 36.9 34.6 37.2 33.2