The purpose of this activity is to help give you a better understanding of the underlying reasoning behind the interpretation of confidence intervals. In particular, you will gain a deeper understanding of why we say that we are “95% confident that the population mean is covered by the interval.”

Launch the applet in a separate window.

The applet has a new look and different ways of entering the information but otherwises, works the same and still illustrates the same concepts.

Transcript – Video of Confidence Interval Applet in Action

When the applet loads, you see a normal-shaped distribution, which represents the sampling distribution of the mean (x-bar) for random samples of a particular fixed sample size, from a population with a fixed standard deviation of σ (sigma).

The green line marks the value of the population mean, μ (mu).

Learn By Doing
Question prompt


  1. The number of courses the student takes this semester:
  2. The student's height:
  3. The student's (exact) body temperature:
  4. The number of siblings the student has:
  5. The (exact) time the student spends doing school work during a week:
  6. The number of alcoholic beverages that the student drinks in a typical week:
A Choice 1
B Choice 2
C Choice 3
D Choice D
E Choice E
F Choice F
G Choice G
H Choice H
Our Answer Comments.