# Help with probability density function

#### louise113

##### New member
Hello,

I am struggling with the following question -does anyone have any ideas on how to approach it?

Y has the probability density function defined by: f(y) = kθ^k / y^k+1, y >= θ

and f(y) = 0 for y< θ, where θ>0 and k>0

Question: Why is k restricted to being greater than 2 in the definition of the pdf?

Thanks

#### tkhunny

##### Moderator
Staff member
Have you considered testing for a valid probability density? Maybe an integral to see that it adds up to Unity? You may find restrictions along the way.