The Group by operator provides the Standard deviation aggregation in Eventstream
Ingest and transform streaming data
AnswerCorrect answer: B - The Eventstream Group by operator includes Standard deviation in its aggregations, while Aggregate only offers Average, Max, Min, and Sum.
You have a Fabric workspace that contains an eventstream named Eventstream1. Eventstream1 processes data from a thermal sensor by using event stream processing, and then stores the data in a lakehouse. You need to modify Eventstream1 to include the standard deviation of the temperature. Which transform operator should you include in the Eventstream1 logic?
100% of anonymous learners picked answer B.
Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
In the Eventstream event processor, Standard deviation is available only in the Group by operator, not in Aggregate - a deliberate trap between the two aggregation operators.
To add the standard deviation of the temperature in Eventstream1, use the Group by transform operator, whose aggregation list includes Standard deviation; the Aggregate operator only offers Average, Max, Min, and Sum.
Choosing Aggregate because standard deviation is conceptually an aggregation; in Eventstream the Aggregate operator exposes only Average, Max, Min, and Sum.
Community Discussion (5 comments)
GHill1982👍 7Selected: B
The Group by transform operator contains the Standard deviation aggregation. The Aggregate transform operator only contains Average, Max, Min and Sum aggregation.
Standard Deviation is only available in Group by, not Aggregate operator
MultiCloudIronMan👍 1Selected: D
while Group by is useful for creating groups, it does not provide the full range of aggregate functions that Aggregate does, including the standard deviation. This is why the Aggregate operator is the correct choice.
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Expert Analysis
Why the Answer Is Correct
The Eventstream event processor's Group by operator includes Standard deviation in its aggregation functions, so adding a Group by transform over the temperature field produces the required standard deviation. Microsoft's event processor documentation lists Standard deviation among the Group by aggregations, while the simple Aggregate operator exposes only Average, Max, Min, and Sum.
Why the Other Options Are Wrong
Option D (Aggregate) cannot compute standard deviation because it only offers Average, Max, Min, and Sum. Option A (Expand) flattens arrays or records into separate rows or columns and performs no aggregation. Option C (Union) combines events from multiple streams and does no aggregation either.
Community Comment Notes
The community strongly favors B (93 votes). GHill1982 (7 likes) states the Group by operator contains the Standard deviation aggregation while Aggregate only has Average, Max, Min, and Sum, and 405a659 links the event processor editor documentation confirming it.