Tools like SAS Visual Analytics and similar use terms like outlier and maximum and I wasn’t sure of the difference.

Today, I was looking at Box plots and while I could see the difference between an outlier and a maximum, I didn’t really know how each is calculated. Here goes….

While mean, medium and percentile are fairly clear, I’m not sure how the **Max**imum and **outlier** are calculated.

SAS defines the maximum and outlier as:

Outlier:an observation outside the lower and upper fences. The fences are located at a distance 1.5 times the Interquartile Range (IQR = Q3 – Q1) above and below the box

Max:maximum data value less than or equal to the upper fence.

Where:

**IQR** (inter quartile range) = Q3 – Q1

**Q1** – 1st quartile (25th percentile). The data must contain a nonmissing value for this quartile.

**Q3** – 3rd quartile (75th percentile). The data must contain a nonmissing value for this quartile.

I’m doing a part-time course in Data Analytics at the University of Brighton. Seems like a good excuse to post some stuff here and see if my site gets a new lease of life.

I’ll probably post things on here that I need to know.