The StandardDeviationPopulation Aggregate defined in Table 50 uses the formula:

image008.png

where X is each Good raw value in the interval, Avg(X) is the average of the Good raw values, and n is the number of Good raw values in the interval.

For every interval where n = 1, a value of 0 is returned.

If any non-Good values were ignored, the Aggregate quality is uncertain/subnormal.

All interval Aggregates return timestamp of the start of the interval. Unless otherwise indicated, qualities are Good, Calculated.

This calculation is for a full population where the calculation is done on the full set of data. Use StandardDeviationSample to calculate the standard deviation of a subset of the full population (5.4.3.37). An example would be when the underlying data is collected on an exception basis versus sampled from the data source.

Table 50 – StandardDeviationPopulation Aggregate summary

StandardDeviationPopulation Aggregate Characteristics

Type

Calculated

Data Type

Double

Use Bounds

None

Timestamp

StartTime

StatusCode Calculations

Calculation Method

Custom

Always Good

Partial

Set Sometimes

If an interval is not a complete interval

Calculated

Set Always

Interpolated

Not Set

Raw

Not Set

Multi Value

Not Set

StatusCode Common Special Cases

Before Start of Data

Bad_NoData

After End of Data

Bad_NoData

No Start Bound

No special handing required

No End Bound

No special handing required

Bound Bad

No special handing required

Bound Uncertain

No special handing required