Parents of 14 entering first graders eagerly volunteer their children for the tryout of a new experimental reading program announced at a PTA meeting. To obtain an "equivalent" group for comparison purposes, each experimental child is matched with a child in the regular program on the basis of sex and reading-readiness scores from kindergarten. At the end of the first grade, a dependent-samples t test shows those in the experimental program to have significantly higher reading achievement scores than their matched counterparts in the regular program.

(a) What is the essential difference between this research design and the design described.

(b) Explain any important advantage(s) either design might have over the other.

(c) Provide an alternative possible explanation (other than the experimental reading program itself) for the significantly better scores of the experimental children.