The “word gap” refers to the finding that children raised in households with more resources tend to hear more words at home than do children in households with fewer resources. For example, one study found mean differences by social class in the number of unique words heard per hour by three-year-olds at home.

Table 11.10 gives the number of unique words per hour that five three-yearolds heard at home in the three social class groups.

a. Complete the table and find the within groups sum of squares for each social class category.

b. What is the overall within groups sum of squares for the three social classes shown in Table 11.10?

c. Find the between groups sum of squares.

d. Find the within and between mean squares.

e. Comparing the within mean squares and between mean squares, where do we see more variation in number of words heard per hour: within social class groups or between them?

f. Explain how we can tell whether the difference in variation within and between groups is large enough to declare that differences across classes in number of words heard are “statistically significant”? Are there statistically significant differences?
g. Can you tell which differences are statistically significant?