
Key: DMN13131

Status: open

Source: Red Hat ( Matteo Mortari)

Summary:
The specification in chapter "10.3.4.4 List functions" for builtin function stddev does not explicit if it's meant to be population or sample standard deviation.
However based on the example provided "stddev( 2, 4, 7, 5 ) = 2.0816659994661" would indicate it is meant to be the sample standard deviation which is undefined for a single 1 sample valueIn order to be explicit, it is suggested to change the table entry as:
Name(parameters) Parameter Domain Description Example stddev( list )
stddev( n 1 , ..., n n )list is a list of number. n 1 ... n n are numbers. Returns the
(sample) standard deviation of the list of numbers. If the list is empty,
returns null. If the list contains only one number item, if n is a single number returns null.stddev( 2, 4, 7, 5 ) =
2.0816659994661
stddev( [ 47 ] ) = null
stddev( 47 ) = null
stddev( [ ] ) = null 
Reported: DMN 1.2b1 — Fri, 18 Jan 2019 15:30 GMT

Updated: Tue, 7 May 2019 14:59 GMT
DMN13 — Make explicit reference to sample standard deviation
 Key: DMN13131
 OMG Task Force: Decision Model and Notation 1.3 RTF