what is z score
What Is a Z-Score and How to Calculate It?
If you work with statistics, z-score is one of the most important standardization tools. This guide explains it clearly.
How to calculate using Z-Score Calculator
- Enter observed value, population mean, and standard deviation.
- Compute z-score to locate the observation relative to distribution center.
- Use percentile approximation for practical interpretation.
Z-Score Calculator formula
- z = (x - mean) / standard deviation.
- Positive z means above mean; negative z means below mean.
- Larger absolute z indicates more extreme deviation.
Worked example
- If x=85, mean=70, sd=10, then z=1.5.
- This means value is 1.5 standard deviations above mean.
- Use this in exam analytics, quality control, and research screening.
Accuracy and interpretation notes
- Standard deviation must be greater than zero.
- Ensure units for value and mean are identical.
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