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How to calculate Z-score

The Z-score formula, with plain worked examples you can check yourself.

Z-score = (x − μ) ÷ σ

Worked examples

x = 57.5 · μ = 50 · σ = 5Z-score = 1.5
x = 65 · μ = 50 · σ = 5Z-score = 3
x = 110 · μ = 70 · σ = 20Z-score = 2

How to use it

  1. Write down the values for each letter in the formula.
  2. Do the brackets first, then divide or multiply.
  3. Check the units before you compare results.
  4. Compare the answer with last period or with a competitor to see if it is good or bad.

This formula belongs to Strategy & Decisions.

Related terms

SWOT analysisKPIStakeholderOpportunity costSunk costVision statement

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