Regarding inferences about the difference between two population means, the sampling design that uses a pooled sample variance in cases of equal population standard deviations is based on:

independent samples.

Explanation:

independent samples are randomly selected models so that its findings do not depend on the values of other observations. Many statistical analyzes rely on the assumption that the models are independent. Others are designed to estimate models that are not independent. There are so many independent models that its choices can be randomly selected without relying on the evidence of other observations.