First-born children tend to develop language skills faster than their younger siblings. One possible explanation for this phenomenon is that first-born children 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. In 1937, Davis found exactly this result. The following hypothetical data demonstrate this relationship. The dependent variable is a measure of language skill at age three. Does the data provide evidence for significant differences between the three populations? Test at the .05 level.
Single Child
9
8
9
7
9
Twin Child
7
6
7
4
Triplet Child
3
5
8
1
3
State the null and alternative hypothesis.
Null hypothesis: There is no significant difference in language development between children with different siblings.
Alternative hypothesis: At least one group has a different mean language development score.
Fill in the following table of descriptive statistics.
Descriptive Statistics
Single:
\table[[,N,Mean],[SD,,],[5,8.4,0.8]]