Daily DAX : Day 411 NORM.DIST

Power BI DAX: NORM.DIST Function

NORM.DIST returns the normal distribution (Gaussian bell curve) for a specified mean and standard deviation.

Syntax

NORM.DIST(x, mean, standard_dev, cumulative)

Parameters

Parameter	Description	Required
x	The value at which to evaluate the distribution	Yes
mean	The arithmetic mean of the distribution (center of the bell curve)	Yes
standard_dev	The standard deviation of the distribution (> 0)	Yes
cumulative	Logical value: TRUE = cumulative distribution function (CDF), FALSE = probability density function (PDF)	Yes

Return Value

• If cumulative = FALSE → returns the height of the normal curve at point x (probability density)
• If cumulative = TRUE → returns the probability that a value is less than or equal to x (cumulative probability)

Common Use Cases in Power BI

• Calculate the probability that a sales amount, test score, or production measurement falls within a certain range
• Create dynamic banding (e.g., flag values that are > 2 standard deviations from the mean)
• Build statistical KPIs like "Percentage of customers within target range"
• Simulate confidence intervals or forecast ranges in reports

Practical Examples

1. Probability a sales rep is below target (cumulative)

Prob Below Target = 
NORM.DIST(
    [Actual Sales],
    100000,        // average sales
    20000,         // standard deviation
    TRUE           // cumulative
)

2. Flag outliers (> 2 standard deviations above mean)

Is Outlier = 
IF(
    [Sales] > 
    100000 + 2 * 20000 + 0.01,      // slightly above 2σ to avoid floating point issues
    "Yes",
    "No"
)

// Or using NORM.DIST for probability-based flagging:
Probability = NORM.DIST([Sales], 100000, 20000, TRUE)
Is Extreme = IF([Probability] > 0.9772 || [Probability] < 0.0228, "Yes", "No")  // ≈ ±2σ

3. Probability density (rarely used in visuals, useful in calculations)

Density = NORM.DIST([Value], [Mean], [StdDev], FALSE)

Related Functions

• NORM.INV – inverse of NORM.DIST (given probability, find x)
• NORM.S.DIST – standard normal distribution (mean=0, stdev=1)
• NORM.S.INV – inverse of standard normal

NORM.DIST is one of the most useful statistical functions in Power BI when building advanced analytics dashboards.