Z-scores

Hi there I am really struggling with z-scores. I know the basics, so how to get the z-score from using the mean, raw score and then dividing by the SD.But when it comes to questions like this I'm completely stumped:I

n an IQ distribution, where the mean is 100 and the standard deviation is 15,
a) what IQ score are 95% of people above?
b) what percentage of people would score less than 90?
c) what z score does a person have who scores 120?If anyone could explain this I'd be really grateful. Thanks in advance

Reply 1

username2130115

16

Original post by Juuuuh

Hi there I am really struggling with z-scores. I know the basics, so how to get the z-score from using the mean, raw score and then dividing by the SD.But when it comes to questions like this I'm completely stumped:I

n an IQ distribution, where the mean is 100 and the standard deviation is 15,
a) what IQ score are 95% of people above?
b) what percentage of people would score less than 90?
c) what z score does a person have who scores 120?If anyone could explain this I'd be really grateful. Thanks in advance

a) form an equation. e.g. P(Z>z) = 0.95. use the tables to find z then use the conversion formula
b) similar to a. (psychology tells us the answer is 25%)
c) use the conversion formula.