# Need Help Badly

1. Jun 21, 2007

### maria_01

1. The problem statement, all variables and given/known data
The random variable x takes on the values 1, 2, or 3 with probabilities (1 + 3k)/3, (1 + 2k)/3, and (0.5 + 5k)/3, respectively.

2. Relevant equations

i. Find the appropriate value of k.
ii. Find the mean.
iii. Find the cumulative distribution function.

3. The attempt at a solution

2. Jun 21, 2007

### nrqed

As per the guidelines of the forum, you must show your own attempts (some work) before people help you out. It's to make sure we are helping and not doing all the work (and you will truly learn only if you do part of the work yourself).

As a hint for the first question: what should be the sum of the probabibilities of all the possible outcomes?

3. Jun 21, 2007

### maria_01

The the sum of the probabibilities is 1.

4. Jun 21, 2007

### matt grime

And so k is what/satisfies what?

5. Jun 21, 2007

### maria_01

I'm an IT person clueless of statistics. I took an online course and now struggling to understand. If you can help that be great.

Also if I knew how to do it, I wouldn't be asking for help. My attention is not to just get the answers but atleast know which formulas to use and how to imply them. I"m really stuck at cumulative distribution function.

6. Jun 21, 2007

### G01

The rules are, you must show some work! No one is COMPLETELY clueless on a problem. You knew the probabilities summed to 1, so your not completely clueless. Now if you know that the probabilities have to sum to 1, then this should be nothing more than an algebra problem for part A.

If the probabilities sum to 1, what must k be?

7. Jun 21, 2007

### matt grime

THe first part is nothing to do with stats - you have 3 numbers that sum to 1. The second two parts are just plugging numbers into a formula.