Interval Plot: Visualize Means and Confidence Intervals for Comparison
What is an Interval Plot?
An interval plot draws a point for each group mean with an error bar extending to its confidence interval, by default 95%, computed from the t or normal distribution. The interval width reflects the precision of the mean estimate: narrower intervals mean more precise estimates, and non-overlapping intervals between two groups usually hint at a significant difference. It turns the abstract idea of uncertainty into a visual form that lowers the statistical barrier.
When to Use It
Use it when comparing several group means, such as different formulations, process settings or suppliers, when presenting the precision of experimental or survey results, and as a graphical companion to ANOVA. In experiment reports an interval plot shows both the estimate and its precision at once, and comparing groups side by side is very intuitive.
How to Use It (Step by Step)
Paste the grouped data, choose the confidence level (90%, 95% or 99%) and the distribution basis (t or normal), and the tool draws the interval plot and outputs the numeric table of means and intervals. Use the table to quote exact numbers in reports and the AI interpretation to summarize group differences. Formal conclusions still need a hypothesis test.
Key Formulas / Example
The interval is x̄ ± t(α/2, n − 1)·s/√n for the t-distribution. Example: with mean 10.2, s = 1.5 and n = 25, the 95% interval is approximately 9.58 to 10.82. Remember that overlapping intervals do not strictly prove non-significance, so pair the plot with a t-test or ANOVA for the formal conclusion.