File:Wilson score pdf and interval equality.png

Summary
Wallis, Sean. Original image by author, method in https://corplingstats.wordpress.com/2018/09/25/plotting-the-wilson-distribution, also published in Wallis (2021: 297-313).

Example probability density function (pdf) for Wilson score distribution, and Normal pdfs at interval bounds (observed proportion = 0.3, sample size n = 10, two-tailed error level alpha = 0.05). Demonstrates the equality of tail areas (highlighted), termed the 'interval equality principle' (Wallis 2021).