Why is it necessary to use the pooled variance when conducting an independent-samples t test?
A) We are working with two samples, and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample.
B) It is necessary to estimate the standard deviation of the two samples in order to compare the two samples to one another.
C) Estimating the spread of the sample using the standard deviation increases the generalizability of results.
D) Using the pooled variance helps the researcher identify skewness.

Question

Quizplus · Accepted Answer

When conducting an independent-samples t test, it is necessary to estimate the variance of the populations from which the two samples were drawn. Since we only have access to the sample data, we use the sample variances as estimates of the population variances. However, if the two samples have significantly different variances, using either of the sample variances alone as an estimate of the population variance may not be accurate. By pooling the variances, we are able to obtain a more accurate estimate of the population variance, and therefore a more accurate test of whether the means of the two populations are different.

Why Is It Necessary to Use the Pooled Variance When