# Q-test for Rejection of Outliers

## Introduction

The Q-test is a simple statistical test to determine if a data point that appears to be very different from the rest of the data points in a set may be discarded. Only one data point in a set may be rejected using the Q-test. The Q-test is:

The value of Q is compared to a critical value, Q_{c}.

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:

Copyright © 2000 by Brian M. Tissue, all rights reserved.