Answer:
The correct answer is Pooled-variance t test for the difference between two means.
Explanation:
Clustered variance is a method to estimate the variance of several different populations when the average of each population may be different, but it can be assumed that the variance of each population is the same.
Under the assumption of equal population variances, the pooled sample variance provides an estimate of the variance with higher precision than the individual sample variances. This greater precision can lead to an increase in statistical power when used in the contrast of hypotheses that compare populations, such as the Student's t-test.
The square root of a clustered variance estimator is known as a grouped standard deviation (or also as a combined, compound or general standard deviation).
