Go to artofstat.com, click on WebApps and open the Explore Coverage app.Change the tab on top of the graph to Confidence Interval for a Mean. Change the Population Distribution to Bell-shaped and use the default mean=50 and standard deviation=10.

Under Choose confidence level (in %) use the default 95, and under "Select sample size (n)" use the default of n=20. Under Select how many samples (of size n) you want to draw from the population start with just 1. Click on Draw sample(s) and note that a confidence interval appears under the population graph.

What does the red half circle at the bottom of the pagerepresent?

a) The true population mean, which does not change each time we take a sample.

b) The sample mean, which changes each time we take a sample.