What Is the Sample Size — Proportion?
Estimate sample size for a proportion from Z, p and margin of error. The calculator is paired with the governing relationship so the numerical output stays connected to the concept you are studying.
Use Sample Size — Proportion to test worked problems, inspect how changing an input changes the output, and verify your own arithmetic before returning to the underlying concept.
Formula or Method
With Z=1.96, p=0.50 and E=0.05, n≈384.16, so round up to 385. The estimate assumes the planning model and does not automatically account for design effects, nonresponse or finite populations. Keep units and conventions consistent with the problem statement and with the options shown in the calculator.
How to Use the Calculator
- Read the input labels and enter the values requested by the problem, exercise or sequence.
- Check units, signs, angle mode, date convention, population/sample options or other settings before calculating.
- Compare the result with the displayed formula or method and the worked example below.
- Round only at the stage required by the question, course or reference convention.
Worked Example
Common Mistakes
- Using the wrong population/sample or percentile convention.
- Rounding intermediate values before the final calculation.
- Entering duplicated, missing or differently scaled observations unintentionally.
Why It Matters for Students
This tool is useful when a statistical relationship needs a fast numerical check. Keep the dataset, definition and convention visible while practising.
The estimate assumes the planning model and does not automatically account for design effects, nonresponse or finite populations. The interactive calculator is designed to make that relationship easier to verify while studying, not to replace the worked reasoning in a textbook or question stem.
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