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T-Test Formula:
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The t-test for difference between two means is a statistical test that determines whether there is a significant difference between the means of two groups. It calculates a t-value which can be compared against critical values to assess statistical significance.
The calculator uses the t-test formula:
Where:
Explanation: The t-value represents how many standard errors the difference between means is from zero. Larger absolute t-values indicate more significant differences.
Details: The t-test is crucial for comparing two groups in scientific research, quality control, and data analysis. It helps determine if observed differences are likely due to chance or represent true population differences.
Tips: Enter both group means and the standard error of their difference. The standard error must be greater than zero for valid calculation.
Q1: What's the difference between one-tailed and two-tailed t-tests?
A: One-tailed tests check for difference in one direction only, while two-tailed tests check for any difference (more conservative).
Q2: How do I interpret the t-value?
A: Compare your t-value to critical values from a t-distribution table based on your degrees of freedom and significance level (typically 0.05).
Q3: What's the relationship between t-value and p-value?
A: The t-value is used to calculate the p-value, which directly indicates statistical significance (typically p < 0.05 is significant).
Q4: When should I use this t-test versus other versions?
A: This calculator is for independent samples t-test with known standard error. Use paired t-test for related samples or different formulas for unequal variances.
Q5: What are common mistakes in t-test interpretation?
A: Common errors include ignoring assumptions (normality, equal variance), confusing statistical with practical significance, and multiple testing without adjustment.