How are Moving Average and Standard Deviation calculated in MI?
The number of intervals used can be modified
The Moving Average and Standard Deviation always are calculated using trailing; i.e., historical) data. The period that is used for the calculation is determined by the Alert Prior Measurement Value Count setting in the Measurement Interval Editor as shown above.
EXAMPLE: The Moving Average for the data point on 8/1 would be based on the 30 days from 7/3 to 8/1, inclusive. The Moving Average for 8/1 would be based on the 30 days from 7/2 to 7/31, inclusive.
NOTE: We shift the Standard Deviation calculation back by one day so that sudden fluctuations can be compared against a stable historical data set. This is to avoid comparing a big fluctuation against a data set that includes the big fluctuation itself! Сurrent data point is excluded from the moving average calculation.