AS/A2 Stats 1 Stats 3

S2 Topic 2: Continuous random variables
Calculating the quartiles
A pdf f(x) is defined by:
The lower quartile, Q1 of a continuous distribution with pdf f(x) is the value that satisfies:

The upper quartile, Q3 of a continuous distribution with pdf f(x) is the value that satisfies:

Summary The interquartile range = Q3- Q1 = 3.464 - 2 = 1.464. This method uses integration techniques from Pure 1. You will have to apply the above method usually in simple cases, where the pdf f(x) may be linear or in a form conveniently chosen for the problem. This page uses WebEQ. To speed up downloading you can install this WebEQ Math Viewer . Click on the Math Viewer icon and you will be taken to the download site.