Image: Chi-square median approx

Description: This replacement for the en.wikipedia's non-free and not-very-good plot File:Chi on SAS.png (from this blog) shows the numerically computed median of the chi-squared distribution, and the approximation from the Wilson–Hilferty transformation, at integer degrees of freedom (circles) and also as a continuous function that could be transformed to represent the median of the gamma distribution. The median and approximation are too close to see a difference, so their difference (absolute error) is also plotted, and also the relative error, which is difference (median - approx) divided by the true median. For degrees of freedom less than 2/9, the approximation goes negative, so the curves are cut off at that point.
Title: Chi-square median approx
Credit: Own work
Author: Dicklyon
Usage Terms: Creative Commons Attribution-Share Alike 4.0
License: CC BY-SA 4.0
License Link: https://creativecommons.org/licenses/by-sa/4.0
Attribution Required?: Yes