## Q-Test

**Q-test.** Use to identify statistical outliers in data. This test should be applied sparingly and never more than once to a single data set.

R is the range of all data points, *x*_{a} is the suspected outlier, and *x*_{b} is the data point closest to *x*_{a}. At the 90% confidence interval Q for N replicate measurements is:

**Q-Test decision level at 90% confidence interval**
N |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |

Q |
0.94 |
0.76 |
0.64 |
0.56 |
0.51 |
0.47 |
0.44 |
0.41 |