1. Normal Distribution with Graphing Calculator

2. Example
The scores on an IQ test approximate a normal distribution with a mean µ = 100 and standard deviation of σ = 25.
To find a percentage (area) use the NormalCDF command: This can be found by pressing: nd  DISTR
normalCDF(lower bound, upper bound, mean, standard deviation)

3. The scores on an IQ test approximate a normal distribution with a mean µ = 100 and standard deviation of σ = 25.
A) What percentage of all test takers score between 85 and 110?
 38.12%
B) What percentage of all test takers score below 90?
 34.46%
C) What percentage of all test takers score above 120?
 21.19%

4. The scores on an IQ test approximate a normal distribution with a mean µ = 100 and standard deviation of σ = 25.
If you need to find a score given an area: use the invNorm command.
invNorm(area below value, µ , σ)
Example: To be in the top 10% of all test takers, what must you score?
132.04

5. The scores on an IQ test approximate a normal distribution with a mean µ = 100 and standard deviation of σ = 25.
What score is necessary to be in the 25th percentile?
83.14