Field
Reversals that are not errors
Simpson's reversal, the base rate, regression to the mean. Each is normally taught with one famous table. A table is a point; these are swept, so how much of the space behaves that way and how large it can get both have answers.
Simpson's reversal is a region, not a table
The treatment wins in both groups and loses overall. That is normally shown with one famous table, which cannot answer the two questions a reader has — how often, and how large. Swept, it turns out to occupy 31% of the allocation space.
What a positive test is worth
A test that is 90% sensitive and 95% specific sounds accurate. For a condition affecting one person in a thousand, 98% of its positive results are wrong, and a worse test on a commoner condition beats a better test on a rare one.
Regression to the mean
Select the worst performers, measure them again, and they improve. Select the best and they decline. No intervention is required for either, the size of the apparent effect is predictable from the correlation alone, and it is the reason so many things appear to work.