# Thread: Graphing the probability distribution function.

1. ## Graphing the probability distribution function.

Hi,

A quick question, if I have a uniform random variable X with a range (1,2,3,...,n) and mass function given by

$\displaystyle Px(i) = 1/n$

For $\displaystyle i=1,2,3,...,n.$

What does the graph of the probability distribution function Fx actually look like?

Hopefully it's easy to describe...

Edit:

I know it's piecewise constant. It takes the value of 0 for x<1.
and then jumps to a value of 1 at x=1. Does it then jump by 1/2 at x=2 and jump by 1/3 at x=3 so on?

2. Originally Posted by waynex
Hi,

A quick question, if I have a uniform random variable X with a range (1,2,3,...,n) and mass function given by

$\displaystyle Px(i) = 1/n$

For $\displaystyle i=1,2,3,...,n.$

What does the graph of the probability distribution function Fx actually look like?

Hopefully it's easy to describe...

Edit:

I know it's piecewise constant. It takes the value of 0 for x<1.
and then jumps to a value of 1 at x=1. Does it then jump by 1/2 at x=2 and jump by 1/3 at x=3 so on?
Dear waynex,

Since this is a probability distribution function it is not continuous. Please refer to the attachment. Of course the points goes on until i=n.

3. Thanks a million for your reply. Quite literally all we have in the notes regarding the graphing of the pdf is:

Fx can be described in words as follows: it is a right-continuous step
function which increases by jumps of size $\displaystyle p_j$located at $\displaystyle x_j$, j = 1, 2, . . .
So I guess you can see where I came up with my answer in the edit above, so I would have thought that it would increase.

So the value at $\displaystyle x_2$ in the problem above would be 1/2 and not 1+1/2 is that correct?

Thanks again.

4. Originally Posted by waynex
Thanks a million for your reply. Quite literally all we have in the notes regarding the graphing of the pdf is:

So I guess you can see where I came up with my answer in the edit above, so I would have thought that it would increase.

So the value at $\displaystyle x_2$ in the problem above would be 1/2 and not 1+1/2 is that correct?

Thanks again.
Dear waynex,

Yes it is correct. Hope you have understood the ideas clearly.