The NORM.S.INV function in Excel is a vital tool for statisticians and data analysts. It computes the inverse of the standard normal cumulative distribution, allowing users to find the z-score for a given probability. This function plays a key role in hypothesis testing and various statistical analyses, enabling professionals to interpret data effectively.

Syntax

NORM.S.INV(probability)

• probability: A numeric value between 0 and 1. It represents the probability for which the inverse cumulative distribution is to be calculated.

Example #1

NORM.S.INV(0.95)

This function calculates the z-score that corresponds to the 95th percentile of the standard normal distribution. The result is approximately 1.645.

Example #2

NORM.S.INV(0.5)

Here, the function returns the z-score for the 50th percentile, which is 0. This indicates that 50% of the data lies below the mean in a standard normal distribution.

Example #3

NORM.S.INV(0.025)

This call provides the z-score for the 2.5th percentile, resulting in approximately -1.96, which is useful for finding critical values in hypothesis testing.

Error handling

• NUM! This error occurs if the input probability is less than 0 or greater than 1, as the function requires a valid probability input.
• VALUE! This happens if the input is non-numeric, meaning that the function couldn’t interpret the provided argument as a valid number.

Conclusion

The NORM.S.INV function is essential for those engaged in statistical analysis, enabling the calculation of critical values from the standard normal distribution. Its utility in rigorous data interpretation and hypothesis testing makes it a fundamental component in environments requiring precise statistical insights.