A kind of interesting discrete random variable is introduced, its mathematical expectation and variance are equal to 1, and further we obtain some summation formulas.是什么意思_A kind of interesting discrete random variable is introduced, its mathematical expectation and variance are equal to 1, and further we obtain some summation formulas.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句