Upgrading from:

Statistics`HypothesisTests`

All functionality is available in the newly created Hypothesis Testing Package.

Load HypothesisTesting` to use the Hypothesis Testing Package functionality:

Version 5.2 << Statistics`HypothesisTests`; MeanTest[{1, 4, 2, 5, 10}, 5]

The KnownVariance option replaces KnownStandardDeviation:

Version 5.2 << Statistics`HypothesisTests`; MeanTest[{1, 4, 2, 5, 10}, 5, KnownStandardDeviation -> 2]