Question

已知随机变量只能取三个值x1,x2,x3,其概率依次成等差数列,求公差d的取值范围

Answer 1

3P1 + 3d = 1

d = 1/3 - P1

P1 > 0

so d < 1/3

P1 < 1

so d > -2/3