Chapter 12

Deciphering Your Confidence Interval


Bullet Correctly interpreting the results of a confidence interval

Bullet Avoiding common interpretation mistakes

Bullet Knowing what confidence intervals don’t measure

Confidence intervals can be straightforward, black-and-white calculations (with practice), yet their real meaning can still remain a mystery. With the guidance in this chapter, I help you avoid making the mistakes that drive instructors (and, subsequently, you) crazy. You can become one of the enlightened who “get it” and thereby get more points on exams. Because in the end, it’s all about points, isn’t it?

Interpreting Confidence Intervals the Right Way

Because I’ve been a statistics professor for many years, I know how disappointed instructors can get when students don’t completely understand what the results of a confidence interval really mean. (Part of it is our own fault because we have a hard time explaining it clearly ourselves.) Instructors want to harp and wax philosophic on this issue to no end, and we make it a personal challenge to help you understand it. In other words, confidence intervals show up on every quiz or exam that instructors can possibly include ...

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