设15000件产品中有1000件次品，从中抽取150件进行检查，则查得次品数的数学期望为______．

解题思路：根据15000件产品中有1000件次品，得到本产品出现次品的概率，从中抽取150件进行检查，要求查得次品数的数学期望，只要用次品出现的概率乘以抽取的件数．

∵15000件产品中有1000件次品，
从中抽取150件进行检查，
∴查得次品数的数学期望为150×
1000
15000＝10．
故答案为10．

点评：
本题考点： 离散型随机变量的期望与方差．

考点点评： 让学生进一步理解期望是反映随机变量在随机试验中取值的平均值，它是概率意义下的平均值，不同于相应数值的算术平均数．区别随即机变量的期望与相应数值的算术平均数．

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