Confidence Interval Calculator for the Difference Between Independent Means
This confidence interval calculator provides full details of the calculation for the difference between two independent sample means, including individual sample statistics, pooled variance, and the confidence interval.
Further Information
This calculator computes the confidence interval for the difference between two independent sample means. This is useful when you want to estimate the likely range for the true difference between two population means.
When to Use
- Two independent samples
- Comparing means from two different groups
- Both samples are approximately normally distributed
- Samples have roughly equal variances (or use Welch's approximation)
Equation
CI = (M₁ - M₂) ± (tα/2 × SEdiff)
Where M₁ and M₂ are the sample means, tα/2 is the critical t-value, and SEdiff is the standard error of the difference.
Standard Error of Difference
SEdiff = √[s²p × (1/n₁ + 1/n₂)]
Where s²p is the pooled variance, calculated as (SS₁ + SS₂) / (n₁ + n₂ - 2).
