# How to Use NORM.S.DIST in Excel for Z-Score Probabilities The `NORM.S.DIST` function in Excel gives you probabilities for the **standard normal distribution** (mean = , standard deviation = 1). The syntax is: ``` =NORM.S.DIST(z, cumulative) ``` - `z`: The Z-score value. - `cumulative`: Enter `TRUE` to get the cumulative probability (area **to the left** of z). --- ## a. Probability Z < -1.25 **Question:** What is the probability that a data point will have a z score less than -1.25? **Excel Formula:** ``` =NORM.S.DIST(-1.25, TRUE) ``` This gives the probability that Z is **less than -1.25**. --- ## b. Probability Z > .5 **Question:** What is the probability that a data point will have a z score greater than +.5? **Step 1:** Find area **to the left** of .5: ``` =NORM.S.DIST(.5, TRUE) ``` **Step 2:** Subtract from 1 to get area **to the right**: ``` =1 - NORM.S.DIST(.5, TRUE) ``` This gives the probability that Z is **greater than .5**. --- ## c. Probability 1 < Z < 2 **Question:** What is the probability that a data point will have a z score between +1 and +2? **Step 1:** Find area **to the left** of 2: ``` =NORM.S.DIST(2, TRUE) ``` **Step 2:** Find area **to the left** of 1: ``` =NORM.S.DIST(1, TRUE) ``` **Step 3:** Subtract: ``` =NORM.S.DIST(2, TRUE) - NORM.S.DIST(1, TRUE) ``` This gives the probability that Z is **between 1 and 2**. --- ## Summary Table | Situation | Excel Formula | |-------------------|------------------------------------------------| | Z < -1.25 | =NORM.S.DIST(-1.25, TRUE) | | Z > .5 | =1 - NORM.S.DIST(.5, TRUE) | | 1 < Z < 2 | =NORM.S.DIST(2, TRUE) - NORM.S.DIST(1, TRUE) | --- Let me know if you want help interpreting the results or understanding the logic!