The correct answer is A. T test.
A t-test is a statistical test that is used to compare the means of two groups. It is a parametric test, which means that it assumes that the data are normally distributed. The t-test can be used to compare the means of two groups that are independent of each other, or it can be used to compare the means of two groups that are related to each other.
Anova is a statistical test that is used to compare the means of three or more groups. It is a parametric test, which means that it assumes that the data are normally distributed. Anova can be used to compare the means of three or more groups that are independent of each other, or it can be used to compare the means of three or more groups that are related to each other.
X2 is a statistical test that is used to compare the observed frequencies of a categorical variable to the expected frequencies of the variable. It is a nonparametric test, which means that it does not make any assumptions about the distribution of the data. X2 can be used to test the independence of two categorical variables, or it can be used to test the goodness of fit of a categorical variable to a hypothesized distribution.
Factorial analysis is a statistical technique that is used to analyze the relationships between two or more variables. It is a multivariate technique, which means that it can analyze the relationships between multiple variables at the same time. Factorial analysis can be used to identify the underlying factors that are responsible for the observed relationships between the variables.
In conclusion, the correct answer to the question “To test null hypothesis, a researcher uses:” is A. T test.