Why not just run many t-tests? ANOVA and multiple comparisons
You have groups (say returns under different signals) and want to know whether their means differ.
Why is running every pairwise t-test a mistake, and what should you do instead?
Show a hint
Each test has its own chance of a false positive. What happens to the combined chance when you run many of them?
Your answer
This one is open-ended. Work it through, then check your reasoning against the full solution.