Chi-平方係種或然率分佈，係Gamma分佈 α = n / 2 , β = 1 / 2 {\displaystyle \alpha =n/2,\beta =1/2} 時嘅特例，模擬 n 個正態分佈亂變量(random variable)嘅平方和 Z 1 2 + ⋯ + Z n 2 {\displaystyle Z_{1}^{2}+\cdots +Z_{n}^{2}} 。
