Answer:One way to compare the variability of two populations is to use the pooled variance, which is a weighted average of the two sample variances.
Explanation:The pooled variance is denoted by s2p and it is calculated as follows:
s2p = [(n1 - 1)s12 + (n2 - 1)s22] / (n1 + n2 - 2)
where n1 and n2 are the sample sizes and s12 and s22 are the sample variances. The pooled variance is the average of the two sample variances when the two populations have the same variance and the two sample sizes are equal. In other words, s2p = (s12 + s22) / 2 when σ12 = σ22 and n1 = n2. This is one condition under which s2p is the average of the two sample variances.