Chisquare distribution facts for kids
In probability theory and statistics, the chisquare distribution is one of the most widely used theoretical probability distributions. It is used in statistical significance tests. It is useful, because it is relatively easy to show that certain probability distributions come close to it, under certain conditions. One of these conditions is that the null hypothesis must be true. Another one is that the different random variables (or observations) must be independent of each other.
Images for kids

Approximate formula for median (from the Wilson–Hilferty transformation) compared with numerical quantile (top); and difference (blue) and relative difference (red) between numerical quantile and approximate formula (bottom). For the chisquared distribution, only the positive integer numbers of degrees of freedom (circles) are meaningful.
See also
In Spanish: Distribución χ² para niños