Comparisons between the respondents and
nonrespondents indicated no statistically significant differences in terms of age, sex, and whether they attended city or rural schools.
Although there was a lower response among families of minority groups (70 %) than among white families (84 %), (p <.01), t - tests and chi - square analyses
indicated that minority - group respondents did not differ from minority - group
nonrespondents on any birth status or sociodemographic variable (p >.05).