4. Differentiating pooled variance and the estimated standard error of the difference in sample means For the independent-measures t test, which of the following describes the pooled variance (whose symbol is )? O A weighted average of the two sample variances (weighted by the sample sizes) O The variance across all the data values when both samples are pooled together O An estimate of the standard distance between the difference in sample means (M1 - M2) and the difference in the corresponding population means (μ1 - µ2) O The difference between the standard deviations of the two samples For the independent-measures t test, which of the following describes the estimated standard error of the difference in sample means (whose symbol ▼ )? is O A weighted average of the two sample variances (weighted by the sample sizes) O The difference between the standard deviations of the two samples