**Aggregation Type** is a parameter that is set while creating a KPI/Measure. It determines what happens to data when viewed using different calendars.

When using the **view calendar** to look at your data, using a calendar period longer than the **data collection calendar** selected to collect data, for example using a Fiscal Year calendar to look at data that is collected monthly, the results are calculated based on **Aggregation Type**.

Aggregation type has four possible values:

**Sum**– Values added monthly will be summed up when viewed quarterly or yearly e.g. Revenue is usually defined as sum.**Average**– Values added monthly will be averaged when viewed quarterly or yearly – e.g. % Customer Satisfaction is usually averaged.**Geometric Mean**– This is a special aggregation often used by statisticians to deal with large variances, see below for more details.**Last Value**– For values added monthly, the last value added will be used when viewed quarterly or yearly – e.g. Cumulative Sales is usually set to last value.

### Geometric Mean

The geometric mean is a special way of calculating the average of multiple numbers used in various statistical models. The technical definition of geometric mean is: The nth root of a product of n numbers.

In practice, the mathematics is fairly simple. With the “average” aggregation type, three numbers are aggregated using (*a* + *b* + *c*) ⁄ 3. For geometric mean, the equation is √ *a* ∗ *b* ∗ *c* .

A geometric Mean is often used to deal with cases where there may be ’outliers’ that skew the data artificially.

For example; let’s say you want to know the “Average number of miles travelled per day” by a truck driver that usually delivers locally. Typically you would record the number of miles per day over a period of one month and divide by the number of ‘driver days’ to give an average.

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