An Excel simulator does twenty samples each flipping a fair coin one hundred times. Each sample generates a confidence interval for the mean number of heads. On average, 19 out of the 20 confidence intervals will include the true mean of 50 heads,
This simulation can be run many times (by pressing F9) and each time a new graph visually updates, showing how confidence intervals work.
The number of flips and the probabilities can all be changed too.