Power Analysis Calculator

Sample size and statistical power for t-tests, ANOVA, and correlation — interactive power curves with a protocol generator for the methods page.

Free · No login · Runs in your browser

1. Protocol Setup

Statistical Test

Solve For

2. Parameters

Cohen's d

0.50Medium

Significance Level (α)

Probability of Type I error (False Positive).

Target Power (1 - β)80%

Required Total Sample Size

128

64 participants per group

Hypothesis Test Visualization

Null Hypothesis (H0)

Alternative (H1)

Power vs. Sample Size

3Study Protocol & Report

Fill in the placeholders below to generate a standardized prose description for your study proposal or manuscript.

Dependent Variable (DV)

Group 1 Label

Group 2 Label

To determine the appropriate sample size for an independent samples t-test comparing Dependent Variable between Group A and Group B, an a priori power analysis was conducted. We aim to detect an effect size of d = 0.5 with 80.0% power at a significance level of α = 0.05 (two-tailed). Based on these parameters, the calculation indicates a total sample size of 128 participants is required (approximately 64 per group) to reject the null hypothesis.

Reference · for the curious

About this material

Statistical power analysis is a critical component of research design and grant proposals. This calculator helps researchers determine the optimal sample size required to detect meaningful effects with sufficient statistical power (typically 80% or higher). It supports common statistical tests including independent and paired t-tests, one-way ANOVA, and Pearson correlation. The tool provides interactive visualizations of the null and alternative hypothesis distributions, as well as power curves to explore the relationship between sample size and power.

Properly powered studies increase the likelihood of reproducible results and are a key requirement for funding agencies like NIH and NSF. Use this tool to generate the statistical methods section of your proposal. For budgeting your study based on sample size, use our Budget Calculator. To ensure your proposal meets formatting requirements, try our Text-to-Space Estimator.