SKEWNESS

Applies to: ✅ Data 360 SQL ✅ Tableau Hyper API

Computes the sample skewness of input values, with a bias correction for finite samples. Skewness measures the asymmetry of a distribution: positive values indicate a longer right tail, negative values indicate a longer left tail, and zero indicates a symmetric distribution.

Syntax

skewness_samp(<expression>)

Arguments

Required

<expression>: An expression of any numerical type.

Returns

Returns a double precision value.

Returns NULL when fewer than three non-null input values are provided or when all non-null values are identical.

Considerations

Use SKEWNESS_SAMP when the data is a sample drawn from a larger population, the typical analytics case. Use SKEWNESS_POP when the data is the complete population of interest.
Uses the adjusted Fisher–Pearson coefficient of skewness, with finite-sample bias correction.
Converges with SKEWNESS_POP for large row counts.
Ignores NULL inputs. Any NaN or infinite input propagates to a NaN result.

Examples

Calculate Sample Skewness

Estimate the skewness of service latency from a sampled slice of requests.

SELECT skewness_samp(latency_ms) AS latency_skew
FROM request_log_sample;

Skewness by Group

Compare the asymmetry of claim amounts across policy lines.

SELECT policy_line, skewness_samp(claim_amount) AS claim_skew
FROM claims
GROUP BY policy_line;

SKEWNESS_SAMP