Final answer:
A Chi-square test is used when a researcher wants to determine if there is a significant difference between observed proportions and expected proportions. So, the correct answer is:D. Chi-square
Step-by-step explanation:
If a researcher wanted to determine whether observed proportions differed significantly from expected proportions, the statistic to be used would be a Chi-square test. This is because the Chi-square test is designed to compare observed frequencies with expected frequencies under the null hypothesis that there are no differences between them. It is helpful in testing for the independence of two factors, goodness-of-fit, and comparing proportions more generally. The null hypothesis for a test of independence asserts that the two factors are not associated. The Chi-square test is always right-tailed, meaning it checks if the observed values are significantly greater than the expected ones, and a large test statistic indicates that there might be a significant difference. The test involves comparing the observed frequencies to the expected frequencies, which are calculated based on the row and column totals in a contingency table.