The T-test formula used here uses which numerator?

• A. Y mean - X mean
• B. X mean - Y mean
• C. Y mean + X mean
• D. Y mean / X mean

Answer: (A)

In a t-test, the numerator is the observed difference between the group means. The common two-sample t-test uses the difference of means as the top part of the statistic, specifically the mean of the Y group minus the mean of the X group. This difference reflects how far apart the groups are, and its sign indicates which group has the higher mean. The magnitude, when divided by the estimated standard error, determines the t value and the resulting p-value. The other options don’t form the appropriate top of the t statistic: a sum is not a measure of difference, and a ratio would be mixing in division rather than representing the difference in means.