The researchers want to determine if preconceptional use of folic acid and race are independent. To do this, they can use a chi-squared test for independence.
The null hypothesis (H0) is that preconceptional use of folic acid and race are independent.
The alternative hypothesis (H1) is that preconceptional use of folic acid and race are not independent.
The chi-squared test statistic can be calculated using the observed frequencies in the table:
White: 260 (yes) + 299 (no) = 559
Black: 15 (yes) + 41 (no) = 56
Other: 7 (yes) + 14 (no) = 21
Total: 282 (yes) + 354 (no) = 636
The expected frequencies under the null hypothesis of independence can be calculated, and the chi-squared test statistic can be computed.
If the p-value is less than a certain significance level (e.g., 0.05), the null hypothesis of independence can be rejected, and it can be concluded that preconceptional use of folic acid and race are not independent.
Without calculating the p-value, it appears that there may be an association between preconceptional use of folic acid and race, as the proportions of women who took folic acid before conception differ across racial groups (e.g., 260/559 = 0.465 for White women, 15/56 = 0.268 for Black women, and 7/21 = 0.333 for women of other races). However, a formal statistical test is needed to confirm this observation.
