*18. You wish to compare the effectiveness of four methods for teaching metacognitive strategies to elementary school children. A group of 40 fifth graders is randomly divided into four subgroups, each of which is taught according to one of the different methods. You then individually engage each child in a \think aloud" problem-solving task, during which you record the number of metacognitive strategies the child invokes. The results are as follows:

Teaching Method 1 2 3 4 n1 ¼ 10 n2 ¼ 10 n3 ¼ 10 n4 ¼ 10 SX1 ¼ 242 SX2 ¼ 295 SX3 ¼ 331 SX4 ¼ 264 S(X  X1)2 ¼ 527:6 S(X  X2)2 ¼ 361:5 S(X  X3)2 ¼ 438:9 S(X  X4)2 ¼ 300:4

(a) Give H0.

(b) Calculate X1, X2, X3, X4, and X.

(c) Compute SSwithin, SSbetween, and SStotal.

(d) Complete the F test (a ¼ :05), state your statistical decision regarding H0, and present your results in a summary table.

(e) Apply the Tukey test (a ¼ :05).

(f) Compute and interpret oˆ 2 from these data.

(g) Draw your final conclusions from these analyses.