This page builds an intuition for what a confidence interval actually means. It is a read-and-play page rather than a problem-solving one, so this worksheet is deliberately short.
There are no recommended tasks for this lesson beyond the interactive page itself. Work down the page from top to bottom, reading all of the material, and complete each Your Task: section — the prompts written in blue — as you reach it.
There are two of them:
- Simulating Confidence Intervals — generate 100 intervals and see how many of them capture the true population mean.
- How Does The Size of a Confidence Interval Vary? — change the confidence level and the sample size, and watch what happens to the width of the intervals.
The second task has its explanation in the drop-downs directly above it. Have a genuine go at the task first, using the sliders to see the effect for yourself, then open the drop-downs to check your reasoning.
The most important idea on this page is what the 95% actually refers to. If you take only one thing away, make it this: the 95% describes how often the procedure succeeds across many samples, not the chance that any one particular interval contains the true population mean.