Page 231 - Statistics for Dummies

Chapter 14
Claims, Tests, and Conclusions
In This Chapter
▶ Testing other people’s claims
▶ Using hypothesis tests to weigh evidence and make decisions
▶ Recognizing that your conclusions could be wrong
ou hear claims involving statistics all the time; the media has no short-
Yage of them:
✓ Twenty-five percent of all women in the United States have varicose
veins. (Wow, are some claims better left unsaid, or what?)
✓ Cigarette use in the U.S. continues to drop, with the percentage of all
American smokers decreasing by about 2% per year over the last ten years.
✓ A 6-month-old baby sleeps an average of 14 to 15 hours in a 24-hour
period. (Yeah, right!)
✓ A name-brand ready-mix pie takes only 5 minutes to make.

In today’s age of information (and big money), a great deal rides on being
able to back up your claims. Companies that say their products are better
than the leading brand had better be able to prove it, or they could face law-
suits. Drugs that are approved by the FDA have to show strong evidence that
their products actually work without producing life-threatening side effects.
Manufacturers have to make sure their products are being produced according
to specifications to avoid recalls, customer complaints, and loss of business.

Although many claims are backed up by solid scientific (and statistically
sound) research, others are not. In this chapter, you find out how to use statis-
tics to investigate whether a claim is actually valid and get the lowdown on the
process that researchers should be using to validate claims that they make.

A hypothesis test is a statistical procedure that’s designed to test a claim.
Before diving into details, I want to give you the big picture of a hypothesis
test by showing the main steps involved. These steps are discussed in the fol-
lowing sections:

1. Set up the null and alternative hypotheses.

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