This web calculator conducts a pooled-variance t-test for a difference between two populations' means when standard deviations are unknown and equal. The calculator includes a video definition, an ...

Specifically, about 68% of those sample means would fall within $4,900 and $5,100 ($5,000 ± $100). About 95% of them would fall within two standard errors ($4,800 to $5,200, or $5,000 +/- $200.

A two-sample z-test for population means compares two population means ... The calculator includes a video definition, an explanation of the formula and practice examples.