1. What is the Mean Difference Interval?

The Mean Difference Interval (Confidence Interval for Mean Difference) estimates the range within which the true population mean difference is likely to fall, with a specified level of confidence (typically 95%).

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \text{Mean Diff} \) — Difference between two means (unit varies by measurement)
• \( t \) — t-value from t-distribution (dimensionless)
• \( SE \) — Standard error of the mean difference (unit varies)

Explanation: The interval provides a range of plausible values for the population mean difference, accounting for sampling variability.

3. Importance of Confidence Intervals

Details: Confidence intervals provide more information than p-values alone, showing both the magnitude and precision of an estimated effect.

4. Using the Calculator

Tips: Enter the mean difference between groups, the appropriate t-value for your confidence level and degrees of freedom, and the standard error of the mean difference.

5. Frequently Asked Questions (FAQ)

Q1: How do I determine the correct t-value?
A: The t-value depends on your desired confidence level (typically 1.96 for 95% CI with large samples) and degrees of freedom (n-1).

Q2: What's the difference between SD and SE?
A: SD measures variability in your sample, while SE estimates how much the sample mean would vary across different samples (SE = SD/√n).

Q3: When should I use this instead of a paired t-test CI?
A: This calculator is for independent samples. For paired data, use a paired t-test confidence interval.

Q4: What does a CI that includes zero mean?
A: If the CI includes zero, there may be no statistically significant difference between groups at your chosen confidence level.

Q5: How does sample size affect the CI?
A: Larger samples produce narrower CIs (greater precision), while smaller samples yield wider intervals.