This is about reading 36: Performance.
CFAI book says that if you widen the confidence band in the quality control chart, you reduce the chance of a type 1 error.
Type 1 error is keeping managers with 0 value added.
But that doesn’t make sense. If you increase the confidence band, you become more tolerant of returns, so you should see an increase in type 1 error.
I’m pretty sure that if you increase the tolerance band, you’re increasing the range of returns you classify as “no talent”.