On a standard IQ test, the scores are normally distributed with a mean of 100 and a standard deviation of 20.
a. if you score 140, in what percentile are you?
b. if you score 90, in what percentile are you?
So i'm pretty sure that i've got the idea behind doing questions like this however to get the final answer i tend to get lost. this is what i'm doing.
x bar = 100 and σ = 20
140 is 40 marks above x bar.
140 is 40/20σ or 2σ above x bar.
now to find the area below 2σ above x bar is where i'm not sure what to do next. Help in this area would be much appreciated.