The aggregation function is part of the definition of the KPI's performance target. The aggregation function tells the system how to merge (or Aggregate) multiple measurements over a number of periods in order to determine whether a party has passed or failed. 


The are a number of ways in which multiple values can be aggregated, each producing a different result. You need to decide which type of aggregation is required to make your KPI target meaningful. The options for the aggregation functions are shown below.


Fig 1 - Options for the Aggregation function


Calculation Differences for Aggregation Functions

In order to demonstrate the difference between each of the aggregation function options, the following measurements are based on a ratio KPI:


Measurement 1: 4/8
Measurement 2: 2/10
Measurement 3: 1/4


The table below shows the calculation that is performed in order to determine the aggregated value.


Tip: When dealing with Ratio Type KPI's, the most common and widely accepted aggregation function is Ratio Total


Function
Calculation
Result
Average( (4/8)+(2/10)+(1/4) ) / 30.316 or 31.6%
Countthere are 3 measurements3
Total(4/8) + (2/10) + (1/4)0.95 or 95%
Ratio Average( (4 + 2 + 1) / 3) / ( (8 + 10 + 4) /3 )

Average of the numerators divided by the average of the denominators
0.318 or 31.8%
Ratio Total(4 + 2 + 1) / (8 + 10 +4 )

Total of the numerators, divided by the total of the denominators
0.318 or 31.8%