Categorical Drift
A PSI of 0.3967 moved the referral rate down 0.44 points. A PSI of 0.0092 moved it up 2.76. The rulebook ranks them the wrong way around.
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Cramér’s V
Twenty categories over two hundred rows, independent by construction, average a V of 0.3077.
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Chi-square (χ²) Test
60% against 56%, scaled from 1,000 rows to 100,000: chi-square goes 1.6420 to 164.2036 and p from 0.2000 to zero.