22. First-born children tend to develop language skills faster than their younger siblings. One possible explanation for this phenomenon is that first-borns have undivided attention from their parents. If this explanation is correct, then it is also reasonable that twins should show slower language development than single children and that triplets should be even slower.

Davis (1937) found exactly this result. The following hypothetical data demonstrate the relationship. The dependent variable is a measure of language skill at age 3 for each child.

Single Child Twin Triplet 86 5 74 5 10 6 8 67 3 94 5 89 4

a. Use an ANOVA with  .05 to determine whether there are any significant mean differences among the three groups of children.

b. Use the Scheffé posttest to determine which groups are significantly different.