People who understand statistics found so occasionally (3)

I believe the answer is:

ons

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'people who understand statistics' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'found so occasionally' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'found'+'so'='foundso'
The alternating letters of 'foundso' are 'ONS'.

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(Another definition for ons that I've seen is " Stages".)

I've seen this clue in The Independent.

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