We value your feedback.

Take our survey and automatically be enter to win anyone of the following:

Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

"Why is it necessary for there to be no outliers in the data for parametric tests."

Because the definition of parametric test (as opposed to non-parmetric) assumes the sample represents a normal population distribution so that simpler statistical methods can be used. Outliers violate this requirement.

See

http://en.wikipedia.org/wi