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Sample Size for a Mean — result sheet
Respondents needed to hit a margin of error at 90/95/99% confidence.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: n = (z* x sd / E)^2, rounded up.
Solve the margin formula for n. Always round up: 216.09 people means 217. Halving the margin quadruples the required sample.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Planning standard deviation — minimum 1.0E-6; maximum 1000000000
- Desired margin of error — Same units as the mean.; minimum 1.0E-6; maximum 1000000000
- Confidence level — 3 choices
Worked example
| Input | Value |
|---|---|
| Planning standard deviation | 15 |
| Desired margin of error | 2 |
| Confidence level | 95 |
217 observations.
Assumptions and limits
- Known or planning sigma; random sampling.
- Two-sided z-interval basis; whole people out.
- Positive sd and margin.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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