sample_stddev
Description
Returns the sample standard deviation of a numerical expression within a group.
- Designed for use cases where substantial values are missing, such as when data is heavily sampled.
Note
Use sample_stddev
when working with incomplete datasets (e.g., sampled trace data). For full datasets, prefer stddev
.
Syntax
Arguments
Name | Type | Required | Description |
---|---|---|---|
expression | number | true | Numerical expression whose sample standard deviation is computed |
Example
Use case: Calculate the standard deviation of API latency in trace data
Traces contain a duration
field representing execution time. Computing its sample standard deviation helps you understand the variability of API performance even when data is incomplete.
{ "operationName": "MalfunctioningDatabase", "duration": 1200 },
{ "operationName": "Scheduled Event", "duration": 32000000 },
{ "operationName": "MalfunctioningDatabase", "duration": 6400 },
{ "operationName": "brokenPrinter", "duration": 10000 },
{ "operationName": "brokenPrinter", "duration": 60000 },
{ "operationName": "ScheduledEvent", "duration": 6000000 },
{ "operationName": "OverloadTable", "duration": 250000 },
{ "operationName": "DownloadInvoiceFunction", "duration": 300000 },
{ "operationName": "MultipleServicesOverload", "duration": 250000 },
{ "operationName": "index.lambda_handler", "duration": 1000000 },
{ "operationName": "DatabaseErrors", "duration": 800 },
{ "operationName": "DatabaseErrors", "duration": 9500 },
{ "operationName": "index.lambda_handler", "duration": 4000000 },
{ "operationName": "HeavyQueries", "duration": 45000 },
{ "operationName": "HeavyQueries", "duration": 120000 },
{ "operationName": "MultipleServicesOverload", "duration": 12000 },
{ "operationName": "DownloadInvoiceFunction", "duration": 90000 },
{ "operationName": "MalfunctioningDatabase", "duration": 8900 },
{ "operationName": "OverloadTable", "duration": 600000 },
{ "operationName": "brokenPrinter", "duration": 120000 }
Output
OperationName | latency_stddev |
---|---|
MalfunctioningDatabase | 4361.089419616654 |
brokenPrinter | 47592.67857298488 |
Scheduled Event | 22761288.829728547 |
MultipleServicesOverload | 83147.67135079544 |
index.lambda_handler | 1638633.7355793486 |
DatabaseErrors | 4238.272307063378 |
HeavyQueries | 59570.23229162531 |
DownloadInvoiceFunction | 152958.53824168033 |
OverloadTable | 139481.44082183167 |
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