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In this article
STANDARDIZE converts a value to a z-score: how many standard deviations it sits from the mean. Z-scores let you compare marks from an easy exam and a hard one.
Syntax
=STANDARDIZE(x, mean, standard_dev)| Argument | What it means |
|---|---|
x |
The value. |
Examples
Example 1
=STANDARDIZE(C2, AVERAGE($C$2:$C$80), STDEV.S($C$2:$C$80))Z-score for each student; above 2 is exceptional.
STANDARDIZE in practice
Where you will use it
- Z-score of a value
- Compare marks across subjects
- Outlier detection
Worked example
| Value | Formula | Result |
|---|---|---|
| 70 | =ROUND(STANDARDIZE(A2,50,10),2) | 2 |
| 50 | =ROUND(STANDARDIZE(A3,50,10),2) | 0 |
| 35 | =ROUND(STANDARDIZE(A4,50,10),2) | -1.5 |
Results calculated in Excel.
Mistakes people make
| Mistake | What to do instead |
|---|---|
| Using sample values | Mean and SD must be calculated first |
| Reading it | Above 2 or below -2 is unusual |
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📎 Practice files for this article
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Free to use for learning. Files with macros (.bas) are plain text — import them with Alt+F11 → File → Import File, and always test on a copy.
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