All AP Statistics Resources
Example Question #1 : How To Find The Quartiles For A Set Of Data
Obtain a normal distribution table or calculator for this problem.
Approximate the -percentile on the standard normal distribution.
The -percentile is the value such that percent of values are less than it.
Using a normal table or calculator (such as R, using the command qnorm(0.9)), we get that the approximate -percentile is about .
Example Question #2 : How To Find The Quartiles For A Set Of Data
Find the first and third quartile for the set of data
In order to find the first and third quartiles, we haave to find the 25th and 75th percentiles, respectively.
To find the percentile, we find the product of and the number of items in the set.
We then round that number up if it is not a whole number, and the term in the set is the percentile.
For this problem, to find the and percentile, we first find that there are 14 items in the set. We find their respective products to be
As such, the and percentiles are the fourth and eleventh terms in the set, or