Inverse Normal
The inverse normal process: given a probability p, find the z-score such that P(Z ≤ z) = p. This requires reverse lookup in normal tables or use of inverse normal functions on calculators.
Real World
University admissions offices use inverse normal to set a grade boundary: if only the top 15% of applicants should receive an offer, they find the z-score where P(Z > z) = 0.15 and back-calculate the required score.
Exam Focus
When finding x from a probability, always find z first using inverse tables, then rearrange x = μ + zσ — show both steps.
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