The StandardDeviationSample Aggregate defined in Table 48 uses the formula:
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 nonGood 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 sample population where the calculation is done on a subset of the full set of data. Use StandardDeviationPopulation to calculate the standard deviation of a full set of data (see 5.4.3.39). An example would be when the underlying data is sampled from the data source versus stored on an exception basis.
Table 48 – StandardDeviationSample Aggregate summary
StandardDeviationSample 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 

Conformance Units 

Aggregates StandardDeviationSample 