Question

Random variable X is normally distributed with mean 10 and standard deviation 2.
Compute the following probabilities.
a. Pr(X<10)
b. Pr(X<11.04)


I don't know where to start.

Answer 1

a) P(X<10) gives a z-score of (10-10)/2 = 0
b) P(X<11.04) gives a z-score of (11.04-10)/2 = .52

You must be given a table of "normal distribution" or have access to a program that duplicates the table or chart.
I use this one
http://davidmlane.com/hyperstat/z_table.html

You can use it directly without finding the z-scores

e.g. for b)
1.
enter: mean: 10 , Sd: 2, click on below and enter 11.04 to get .698468

2.
enter: mean: 0 , Sd: 1 , click on "below" and enter the z-score of .52 to get .698468