Stats help!!!!!!

[fairylight]

OK im prob being really stupid, but i cant for the life of me work out how to do this problem. can someone help???

 

A random variable X takes the integer value x with probability P(X=x) defined by

 

P(X=x) = kx^2, x = 1, 2, 3

P(X=x) = k(7-x)^2 x = 4,5,6

P(X=x) = 0 otherwise

 

Find the value of k

[MandrakeRoot]

Sum of probabilities should be one.

 

Since you have only 6 possible values for x the equation you have to solve is :

 

k + 4k + 9k + k(7 - 4)^2 + k(7 - 5)^2 + k(7 - 6)^2 = 1

which would be

28k = 1, making k = 1/28

 

Mandrake

[Dave]

Beat me to it

 

Works for continuous as well as discrete stuff, except you have to use integration to find the probability density.

[MandrakeRoot]

Or discrete with infinite (but countable) values, needing infinite sums.

 

Mandrake

[Guest lucylooloo]

Thank you sir may I

I am dire need of some assistance in understanding predicting probabilities, I am just lost with most of this

[Dave]

What do you find difficult about them?