Question

The intelligence quotient (iq) test scores are normally distributed with a mean of 100 and a standard deviation of 15. what is the probability that a person would score 130 or more on the test?

Answer 1

                                                        x - 100
Calculate the relevant z-score = ----------------
                                                             15
                            130-100              30
Here, this is z = ----------------- = ----------- = 2
                                     15               15

130 would be 2 std. dev. above the mean here.  

Your job would be to calculate the area under the std. normal curve to the right of z = 2.  Using my TI-83 Plus calculator's built-in normalcdf( function, I found that this probability is 1.00 - 0.977    =    0.023.