# Q-test for Rejection of Outliers

### Introduction

The Q-test is a simple statistical test to determine if a data point that is very different from the other data points in a set can be rejected. Only one data point may be discarded using the Q-test.
Q = |outlier - value closest to the outlier| / |highest value - lowest value|

Table of Q critical values (90% confidence)

N Q_{C}
3 0.94
4 0.76
5 0.64
6 0.56
7 0.51
8 0.47
9 0.44
10 0.41

If Q is larger than Q_{C} the outlier can be discarded with 90% confidence.

### Related topics:

### Further Information

/chem-ed/data/q-test.htm, updated 10/14/96

Copyright © 1996 by Brian M. Tissue, all rights reserved.

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