---
title: "QQ Plots. Data Selection"
canonical: "https://servicedesk.maxgeo.com/space/MAXGEO/1065418804/QQ%20Plots.%20Data%20Selection"
format: markdown
---
1. **QQ plot query**

Two points plotted against each other on the graph are generally NOT the original and repeat from the database. It is a percentile pair. Therefore if grade ranges are used, it is possible for one result of the percentile pair to fall outside the grade range. 


**QQ plot – how is the data selected?**


1. For QQ plots the data is selected based on the Grade range, e.g. for Grade range of 0.3 to 1.5 data is selected where the MEAN of the Original value + Repeat value (to 4dp) is >= 0.3  and < 1.5


1. Then the Original values and Repeat values are sorted separately


1. The lowest Original value is paired with the lowest Repeat value, and so on through to the Highest values, this is then plotted on the QQ chart


1. The net effect is that you may have an Original value AND a Repeat value that are BOTH outside your grade range (they can be lower or higher) that are plotted on the chart


**You can verify this as follow with the Interactive charts:**

1. Select the **Repeat** **Chart** tab
2. Check the **MeanResult** column, all values should fall within the requested grade range, but some of the values from OriginalResult or RepeatResult column which are plotted on the chart will be outside the Grade Range.