If brain cells of a dead fish were tested, can we conclude if it’s dead? When everyone thought running multiple tests would better support our claim, turns out, it rather leads to false conclusions; hence, the name “multiplicity problem”. An overview of classical and modern multiplicity adjustment methods will be introduced controlling Family-wise Error Rate (FWER) and False Discovery Rate (FDR). Software details in R will be demonstrated. Real examples and applications will be presented. Don’t revive a dead fish!

Outline:

1. What is “multiplicity”?
2. When does “multiplicity” arise?
   1. (Example 1) Can dead fish be alive?
   2. (Example 2) Can one drug cure multiple diseases?
3. How can it be handled?
   1. Procedures (Brace yourself for namedropping!)
   2. Dead fish revisited
   3. Drug test revisited
4. How else? (Modern method)
   1. Parallel Gate Keeping