# Thread: Mini prob. question

1. ## Mini prob. question

Given $u = 12$ $o = 3$ , what is the probability of P(X<9) ?

I have no clue how to do it...

2. Am I to assume that u is ${\mu}$ for the mean and

o is ${\sigma}$ for the standard deviation?.

If so, $z=\frac{x-{\mu}}{\sigma}$

$z=\frac{x-12}{3}$

If x=9, then z=-1.

What is the z score for -1?.

3. Is it 0.15?

Why did you find the z score though ?

4. Originally Posted by Faisal2007
Given $u = 12$ $o = 3$ , what is the probability of P(X<9) ?

I have no clue how to do it...
Please post the whole question. Be sure to include the part about what distribution X follows .....

5. Originally Posted by mr fantastic
Please post the whole question. Be sure to include the part about what distribution X follows .....
This is all i have ........... Nothing more or less....

6. Originally Posted by Faisal2007
This is all i have ........... Nothing more or less....
Surely you're told the distribution! What is the context of the question? Is it a question from a problem set on normal distribution? Binomial distribution ....?

If you can't provide all the necessary background information to the question you're not going to get much help.