Normal distribution, Z-Score and Probability Help.

#1
I'm having a difficult time trying to answer these questions. Any help would be very helpful.

The time it takes a randomly selected job applicant to perform a certain task has a normal distribution with mean 120 seconds and standard deviation 12 seconds.

1. We are interested in computing the probability that it takes a randomly selected job applicant more than 135 seconds to perform a task. Compute the Z-Score.

2. Find the probability in question #1.

3. The fastest 10% are to be given advanced training. What task time qualifies individuals for advanced training?
 

Dason

Ambassador to the humans
#2
Hi! :welcome: We are glad that you posted here! This looks like a homework question though. Our homework help policy can be found here. We mainly just want to see what you have tried so far and that you have put some effort into the problem. I would also suggest checking out this thread for some guidelines on smart posting behavior that can help you get answers that are better much more quickly.
 
#3
I'm so sorry.

Well here is what I got and if somebody could tell me if I am going in the right direction.

1.

z=x-m/o

z=135-120/12 = 1.25

2.

using the z table, i went to 1.2 then to .5 and got .8944

3.

I'm not sure how to work it, I'm not really even comprehending this question. 10% of what number?

Thank you all so much for taking time to help me out. I just want to know if I am doing these correctly.