Quartiles and Variance

Hi tmartyn ,

To calculate the variance for each quartile, you can follow these steps:
1. Calculate the Mean for Each Quartile:
You will need to calculate the average (mean) score for each quartile. This can be done by creating a measure that calculates the average for each quartile range.

2. Calculate the Deviation for Each Data Point:
For each data point (score), calculate the deviation from the quartile mean. This is done by subtracting the quartile mean from each score.

3. Square the Deviation:
Square the result of each deviation to get the squared deviation.

4. Sum of Squared Deviations:
Calculate the sum of all squared deviations within the quartile.

5. Calculate the Variance:
Finally, divide the sum of squared deviations by the count of data points in the quartile minus one (n-1) to get the variance.

Quartile Mean = 
AVERAGEX(
    FILTER(
        'YourTable',
        'YourTable'[YourScoreColumn] >= [Percentile P1] &&
        'YourTable'[YourScoreColumn] < [Percentile P2]
    ),
    'YourTable'[YourScoreColumn]
)

Squared Deviation = 
SUMX(
    FILTER(
        'YourTable',
        'YourTable'[YourScoreColumn] >= [Percentile P1] &&
        'YourTable'[YourScoreColumn] < [Percentile P2]
    ),
    POWER('YourTable'[YourScoreColumn] - [Quartile Mean], 2)
)

Variance = 
[Squared Deviation] / 
(COUNTROWS(
    FILTER(
        'YourTable',
        'YourTable'[YourScoreColumn] >= [Percentile P1] &&
        'YourTable'[YourScoreColumn] < [Percentile P2]
    )
) - 1)

Please replace 'YourTable' and 'YourScoreColumn' with the actual names of your table and column. Also, adjust the [Percentile P1] and [Percentile P2] to match the quartile ranges you are using.

Best regards,
Community Support Team_Binbin Yu
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