Solved – Are Family-wise Error and experiment-wise error completely interchangeable terms

hypothesis testingmultiple-comparisonsterminology

Some times I can find in the very same source both terms, but without any explanation.
On the other hand, some paper only use one and some only use the another.
Are these different measures?

Best Answer

I think they should not be regarded as identical; I think the family-wise error rate refers to the overall type I error rate for some specified collection of hypothesis tests, which might potentially be a subset of the tests in an experiment, or even the overall error rate across several experiments (for some reason), or not relate to an experiment at all, while the experiment-wise error rate could only reasonably refer to testing in an experiment and only to the family-wise error rate for that entire experiment.

Which is to say, to my mind the concept of experiment-wise error is a specific example (and perhaps the most common one) of family-wise error.

[What I find interesting is nobody seems to much concern themselves about the type II error rate on a family-wise basis -- at least not that I recall.]

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