FreeTools by FunnyTools.win 繁中

Independent Samples t-test Calculator

🔒 Local only Education & Statistics Tools

Run a Welch independent-samples t test from summary statistics.

Enter N, mean, and sample SD for two independent groups to calculate the mean difference, Welch t, approximate degrees of freedom, and two-tailed p value.

Tool area

Group 1
Group 2

Formula and calculation

t = (M₁ − M₂) / √(s₁²/n₁ + s₂²/n₂)

Degrees of freedom use the Welch–Satterthwaite approximation; p is calculated from the t distribution. s₁ and s₂ are sample SDs.

Educational applications

Use for means from two independent groups. Check independence, outliers, and distribution shape, especially with small or heavily skewed samples. Statistical significance is not the same as educational importance.

APA / research reporting tip

APA example: “Group A (M = 78.4, SD = 8.2) scored higher than Group B (M = 73.1, SD = 9.5), Welch’s t(59.6) = 2.36, p = .022.” Formal reports should add a confidence interval and effect size.

How to use

  1. Enter sample size, mean, and sample SD for both groups.
  2. Confirm observations are independent between groups.
  3. Interpret the difference, t, df, and two-tailed p together.

Use cases

  • Compare mean scores under two teaching methods.
  • Compare treatment and control group means.
  • Check formal software output from summary statistics.

FAQ

Why use Welch’s t test?
It does not require equal group variances and is generally more robust than the pooled-variance version.
Can I enter population SDs?
This calculator expects sample standard deviations.
Does p < .05 mean a large effect?
No. p also depends on sample size; inspect the difference, confidence interval, and effect size.

Related tools

Cronbach Alpha CalculatorEstimate internal consistency from respondent-by-item data.Calculator🔒 Local onlyUse NowNewestZ Score CalculatorConvert a raw score into standard deviations from the mean.Calculator🔒 Local onlyUse NowNewestNormalized Score ConverterLinearly convert a raw score to a target mean and standard deviation.Calculator🔒 Local onlyUse NowNewestGrade Average CalculatorCalculate simple and weighted averages from grade entries.Calculator🔒 Local onlyUse NowNewestPercentile Rank CalculatorCalculate percentile rank from counts below and equal to a score.Calculator🔒 Local onlyUse NowNewestT Score CalculatorConvert a z score to a T score with mean 50 and SD 10.Calculator🔒 Local onlyUse NowNewest
SPSS Levene Test Guide Levene test checks whether group variances can be treated as equal and affects which SPSS t-test row to read.

Privacy & local processing

🔒 This tool runs entirely in your browser. No data is uploaded to any server.

All input and calculations stay in your browser and are not uploaded to FreeTools.

Trust & usage note

This tool runs mainly in your browser. Your input is not actively uploaded to a server. Avoid entering highly sensitive data. Results are for reference only.

Disclaimer

This tool is for teaching and preliminary estimates. It does not replace formal statistical software or professional judgment. Verify the data, research design, and assumptions before reporting results.

Last updated: