How the combined predictor compares with
the individual predictors
On any one test case, some individual predictors will be
better than the combined predictor.
But different individuals will be better on different
cases.
If the individual predictors disagree a lot, the combined
predictor is typically better than all of the individual
predictors when we average over test cases.
So how do we make the individual predictors
disagree? (without making them much worse
individually).