In this section: 
Before creating a new measure, you need to find out:
Critical fields for measures are:
If you have ever tried to aggregate percentages or other results of statistical methods, you may have noticed that it is not possible to accurately aggregate percent or other ratio type metrics. For example, if you have percentage results for defects per thousand for Charlotte at 20% and Toronto at 10%, you cannot simply add the percentages together to get an aggregate of 30%. To aggregate ratios or percentages correctly, PMF performs the following steps for you:
Note: Percent and ratio type measures use separate numerator and denominator fields to let you store and correctly aggregate measures.

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