The NORM.INV function in Excel is a powerful tool designed for statistical analysis. It allows users to find the value at which a given cumulative distribution function of a normal distribution equals a specified probability. This is particularly valuable in fields such as finance, quality control, and many more where understanding probabilities and distributions is crucial.

Syntax

NORM.INV(probability, mean, standard_dev)

• probability: A value between 0 and 1, representing the probability for which you want to find the corresponding value.
• mean: The arithmetic mean of the normal distribution.
• standard_dev: The standard deviation of the normal distribution.

Example #1

NORM.INV(0.95, 100, 15)

This function calculates the value at which the cumulative distribution function is equal to 0.95 for a normal distribution with a mean of 100 and a standard deviation of 15. The result might be approximately 118.54.

Example #2

NORM.INV(0.50, 50, 10)

This function finds the median value of a normal distribution with a mean of 50 and standard deviation of 10. The result would be exactly 50, since it is the mean of the distribution.

Example #3

NORM.INV(0.05, 200, 30)

This function determines the value at which the cumulative probability is 0.05 for a normal distribution with a mean of 200 and a standard deviation of 30. The result could be approximately 167.45.

Error handling

• NUM!: This error occurs when the probability value is not between 0 and 1, or if the standard deviation is less than or equal to zero.
• VALUE!: This error arises when the inputs for mean or standard deviation are not numbers.

Conclusion

In summary, the NORM.INV function is invaluable for performing statistical analysis on normal distributions, allowing users to determine specific values based on cumulative probabilities. By understanding its syntax and parameters, users can effectively implement it in their data analysis tasks to derive meaningful insights.