The distribution of sum-of-squares of k independent standard normal random variables. For the test, use the [chi-squared-test] tag. Use also for related distributions.

In probability theory and statistics, the chi-squared ($\chi^2$) distribution with $k$ degrees of freedom is the distribution of a sum of the squares of $k$ independent standard normal random variables. It is one of the most widely used probability distributions in inferential statistics (for example, in hypothesis testing or in construction of confidence intervals).

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