问题
问答题
设随机变量X的分布列为
| X | -1 | 0 | 1 | 2 |
| P | 0.1 | 0.3 | 0.2 | 0.4 |
答案
参考答案：解 EX=(-1)×0.1+0×0.3+1×0.2+2×0.4=0.9．
DX=(-1-0.9)2×0.1+(0-0.9)2×0.3+(1-0.9)2×6.2+(2-0.9)2×0.4=1.09．
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设随机变量X的分布列为
| X | -1 | 0 | 1 | 2 |
| P | 0.1 | 0.3 | 0.2 | 0.4 |
参考答案：解 EX=(-1)×0.1+0×0.3+1×0.2+2×0.4=0.9．
DX=(-1-0.9)2×0.1+(0-0.9)2×0.3+(1-0.9)2×6.2+(2-0.9)2×0.4=1.09．
Beijing Sunshine Secondary School offers after-school clubs and activities from Monday to Friday. These activities are offered to all of the students at no cost. The school decides to give its students opportunities机会 to become successful lifelong learners.
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