Given E[X]=0.95. Find the probability that X is greater than E[X].

x -1 0 1 2 3

P(X=x) 0.35 0.05 0.1 0.3 0.2

Unsure what's asking me there.

thanks for the help!

Printable View

- Apr 13th 2010, 01:56 AMBabyMiloDiscrete Random Variables
Given E[X]=0.95. Find the probability that X is greater than E[X].

x -1 0 1 2 3

P(X=x) 0.35 0.05 0.1 0.3 0.2

Unsure what's asking me there.

thanks for the help! - Apr 13th 2010, 02:28 AMlosm1
Maybe $\displaystyle P(X>0.95) = 1 - P(less\ then\ 0.95) = 1 - P(-1) + P(0) = 1 - 0.4 = 0.6$ ?

- Apr 13th 2010, 02:35 AMFailure
Well, exactly what they say, I suppose, i.e. they want to know

$\displaystyle P(X>E[X]){\color{red}=}P(X>0.95)=P(X \in \{1,2,3\})$

$\displaystyle =P(X=1)+P(X=2)+P(X=3)=0.1+0.3+0.2=0.6$.

BTW. It's a bit strange that they tell you what $\displaystyle E[X]$ is, because from the given values and probabilities of X one can easily determine the expected value. - Apr 13th 2010, 02:37 AMArchie Meade
- Apr 13th 2010, 02:39 AMlosm1