{ “title”: “VAR_SAMP,VARIANCE_SAMP”, “language”: “en” }

Description

The VAR_SAMP function calculates the sample variance of a specified expression. Unlike VARIANCE (population variance), VAR_SAMP uses n-1 as the divisor, which is considered an unbiased estimate of the population variance in statistics.

Alias

  • VARIANCE_SAMP

Syntax

VAR_SAMP(<expr>)

Parameters

ParameterDescription
<expr>The column or expression to calculate sample variance for, supports type Double.

Return Value

Returns a Double value representing the calculated sample variance. If there is no valid data in the group, returns NULL.

Examples

-- Create sample table
CREATE TABLE student_scores (
    student_id INT,
    score DECIMAL(4,1)
) DISTRIBUTED BY HASH(student_id)
PROPERTIES (
    "replication_num" = "1"
);

-- Insert test data
INSERT INTO student_scores VALUES
(1, 85.5),
(2, 92.0),
(3, 78.5),
(4, 88.0),
(5, 95.5),
(6, 82.0),
(7, 90.0),
(8, 87.5);

-- Calculate sample variance of student scores
SELECT 
    VAR_SAMP(score) as sample_variance,
    VARIANCE(score) as population_variance
FROM student_scores;

+------------------+---------------------+
| sample_variance  | population_variance |
+------------------+---------------------+
| 29.4107142857143 |   25.73437500000001 |
+------------------+---------------------+