Sample Size and Power Calculators
Margin of Error Calculator
Margin of Error Calculator calculate margin of error.
Sample Size and Power Calculators
Margin of Error Calculator
Calculate margin of error.
Formula
Proportion margin of error = z critical * sqrt(planning proportion * (1 - planning proportion) / sample size).
About the Margin of Error Calculator
Calculate margin of error. Planning calculators connect effect size, precision, alpha, power, group count, and sample size for the specific design shown.
How the Margin of Error Calculator Works
Proportion margin of error = z critical * sqrt(planning proportion * (1 - planning proportion) / sample size).
The calculation runs in your browser. Submitted values are validated for the required numeric range, data shape, units, and method-specific restrictions before a result is shown.
Required Inputs
- Sample size (required)
- Planning proportion (required)
- Alpha (required)
Results Reported
The result panel shows the final answer together with the intermediate quantities needed to audit the calculation. Depending on this method, reported values include:
methodsample_sizeplanning_proportionalphaconfidence_levelz_criticalmargin_of_errormargin_of_error_percent
Margin of Error Calculator Example
Use the example data button to load a known sample, then calculate and review the statistic, p-value or estimate, and interpretation.
| Input | Example value |
|---|---|
| Sample size | 385 |
| Planning proportion | 0.5 |
| Alpha | 0.05 |
How to Use the Calculator
- Confirm that the calculator title and method match the quantity, test, conversion, or planning question you need to solve.
- Enter values with compatible units and the requested sample, group, matrix, count, date, or option format.
- Select Example Data to inspect a valid input layout, or enter your own values and select Calculate.
- Review the result table, formula, worked substitutions, warnings, and interpretation rather than using only the headline number.
- Use Copy Result or Download CSV when you need a reusable record of the displayed calculation.
Understanding the Result
Planning assumptions should be justified before data collection; attrition, clustering, unequal allocation, and multiplicity may require a larger design.
Keep the entered values, units, selected options, and any warning shown beside the result. For a hypothesis test, report the statistic, degrees of freedom where applicable, p-value, alpha level, effect size, and decision. For an estimate or conversion, report the formula convention and final unit.
Accuracy and Limitations
The calculator keeps full browser precision during calculation and rounds only for display. Accuracy still depends on correct inputs and on whether the displayed model represents the real problem. Educational calculators cannot replace required professional review, current official rules, field measurements, laboratory methods, or specialist statistical software where those are necessary.
Frequently Asked Questions
What does the Margin of Error Calculator calculate?
Calculate margin of error.
Which formula does the Margin of Error Calculator use?
Proportion margin of error = z critical * sqrt(planning proportion * (1 - planning proportion) / sample size).
What input does this calculator need?
The calculator form shows the required values and validates them before calculating.
Are the formulas visible?
Yes. Each calculator displays its method, assumptions, and interpretation unless disabled by the site administrator.