Sample Size and Power Calculators
Power Calculator for T Test
Power Calculator for T Test estimate power for a t test.
Sample Size and Power Calculators
Power Calculator for T Test
Estimate power for a t test.
Formula
Two-sample t-test power is the probability that a noncentral t statistic crosses the selected rejection boundary, with noncentrality d*sqrt(n/2) and df = 2n - 2.
About the Power Calculator for T Test
Estimate power for a t test. Planning calculators connect effect size, precision, alpha, power, group count, and sample size for the specific design shown.
How the Power Calculator for T Test Works
Two-sample t-test power is the probability that a noncentral t statistic crosses the selected rejection boundary, with noncentrality d*sqrt(n/2) and df = 2n - 2.
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
- Cohen d effect size (required)
- Sample size per group (required)
- Alpha (required)
- Alternative hypothesis (required) Options: Two-tailed, Greater than, Less than
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:
methodeffect_size_dsample_size_per_grouptotal_sample_sizedfalphatail_typecritical_tnoncentrality_parameterexact_powerpower
Power Calculator for T Test 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 |
|---|---|
| Cohen d effect size | 0.5 |
| Sample size per group | 64 |
| Alpha | 0.05 |
| Alternative hypothesis | two |
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 Power Calculator for T Test calculate?
Estimate power for a t test.
Which formula does the Power Calculator for T Test use?
Two-sample t-test power is the probability that a noncentral t statistic crosses the selected rejection boundary, with noncentrality d*sqrt(n/2) and df = 2n - 2.
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.