To investigate three approaches to problem solving, 30 six-graders were assigned to three treatment conditions T1, T2, T3 . Where T1 = control, and T2 and T3 are two experimental conditions. The control group subjects received no training while T2 received film-and-discussion training, while T3 received practical training. At the conclusion of the study, the number of solutions proposed summed across five problems were researched. The Wallach and Kogan's test of association thinking was administered before the experiment. The data follows:

          Y : 11, 12, 19, 13, 17, 15, 17, 14, 13, 16
T1
         X : 21, 23, 25, 23, 23, 24, 24, 20, 22, 24

         Y : 11, 14, 10, 9, 12, 13, 10, 8, 14, 11
T2
         X : 21, 24, 21, 20, 23, 24, 23, 21, 25, 24

         Y : 7, 18, 16, 11, 9, 10, 13, 14, 12, 12
T3
        X : 21, 26, 25, 21, 22, 23, 25, 24, 24, 23

Use an ANCOVA model to analyze these data

a) State model and model assumptions

b) What is the null hypothesis

c) Analyze the data

d) Summarize your findings