问题描述:
1、一组数的平均数是8,标准差是2.5.如果x在这组数中,而且比平均数高了2个标准差,x值是多少?(答案是13)
2、有多少个3位正整数是奇数,并且不含5在任何一位中?(答案是288)
3、Let A,B,C and D be events for which P(A or B) =0.6,P (A)= 0.2,P(C or D)=0.6,an P(C)= 0.5.The event A and B are mutually exculsive,and the events C and D are independent.
求P(B)和P(D)
P(B)我会算,就是0.6-0.2.
我觉得P(D)应该也是0.6-0.5呀,可是答案是0.2.
2、有多少个3位正整数是奇数,并且不含5在任何一位中?(答案是288)
3、Let A,B,C and D be events for which P(A or B) =0.6,P (A)= 0.2,P(C or D)=0.6,an P(C)= 0.5.The event A and B are mutually exculsive,and the events C and D are independent.
求P(B)和P(D)
P(B)我会算,就是0.6-0.2.
我觉得P(D)应该也是0.6-0.5呀,可是答案是0.2.
问题解答:
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