The `NORM.S.INV` function in Excel is used to find the inverse of the standard normal cumulative distribution for a given probability. In simpler terms, it tells you the z-score (or standard score) associated with a given cumulative probability in a standard normal distribution, which has a mean of 0 and a standard deviation of 1.
Syntax
NORM.S.INV(probability)
Parameters
- probability: A probability corresponding to the normal distribution. It should be between 0 and 1.
Usage
To use `NORM.S.INV`, you simply specify the probability for which you want to find the z-score. Here are the steps:
=NORM.S.INV(0.975)
- Select a cell where you want the result to be displayed.
- Enter the formula: Type `=NORM.S.INV(` followed by the probability value. For example, to find the z-score for a probability of 0.975, you would enter:
- Press Enter: After typing the formula, hit the Enter key. Excel will calculate and display the z-score corresponding to the specified probability.
Example
If you want to find the z-score that corresponds to the 97.5th percentile (0.975) of a standard normal distribution:
- Enter the formula `=NORM.S.INV(0.975)` in a cell.
- After pressing Enter, Excel will return approximately 1.96, which is the z-score.
Notes
- The function will return a `#NUM!` error if the probability is less than 0 or greater than 1 because it’s outside the valid range for a probability.
- The result represents how many standard deviations an element is from the mean of the standard normal distribution corresponding to the given probability.
This function is handy for statistical analysis where standard normal distribution values are involved, especially in hypothesis testing and confidence interval calculations.
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