The t-test compares the means of two groups to determine if they are significantly different.
H₀: μ₁ = μ₂ (no difference). If |t| > 1.96, reject H₀ at 95% confidence.
Welch's t-test is used here — no assumption of equal variances.
This calculator is appropriate for any analysis that will be presented, reported, or used to make decisions. Accurate statistical metrics are the foundation of valid conclusions.
A frequent mistake is computing statistics on a dataset without checking for data entry errors, outliers, or missing values. A single transcription error in a small dataset can shift the mean and standard deviation substantially. Always verify the input data before interpreting results.
A quality engineer analyses the diameter measurements of 25 machined parts: mean 50.02 mm, standard deviation 0.08 mm. With a tolerance of ±0.25 mm, the process is well within specification — and the SD confirms the manufacturing variation is low enough that virtually no parts will fall outside tolerance.
A t-test compares the means of two groups. If the t-statistic exceeds the critical value, the difference is statistically significant.
p < 0.05 is the conventional threshold for statistical significance.
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