Question

The random variable X follows a normal distribution of mean=30 and standard deviation of 10. How can I find the probability of X<23?

Answer 1

find the zscore
then, lookup area in ztable

Answer 2

http://www.wolframalpha.com/input/?i=P%28Z%3C%2823-30%29%2F10%29

Answer 3

I did not know what was the z score until now...thanks a lot :)

Answer 4

np :)

Zscore = (observation - mean)/deviation

Answer 5

What is the use of a z score table? (how does it work?)

Answer 6

its just a table