1. Section 10.3Making Sense of Statistical Significance AP Statistics

2. Choosing a level of significance(alpha level) • How plausible is H0? • Depending on H0 plausibility, you may choose a smaller alpha. • If H0 is very plausible, you will need to have collect “more” evidence to reject it. • Example: “You can eat as much as you want and lose weight, as long as you avoid grain products.”

3. What are the consequences of rejecting H0? • If rejecting H0 would • costs lots of money • possibly cost lives • costs jobs • then alpha is usually very small • Example: Global Warming

4. Fishing for significance • Let’s say were trying to find a connection between eating habits and intelligence. • Choose 40 foods, and assign people to increase the amount of the foods they eat, and see if there are any foods that make people smarter. • Of the 40 foods, we find that peeps and green beans make you smarter with alpha=.05. Is this a problem?

5. Fishing for Significance • Yes, this is a problem. • When using alpha=.05 we would expect that by pure chance variation we get significant results once every 20 times. • With 40 foods being tested, about 2 of the foods would have significant results by pure chance.

6. Assignment • 10.57-10.65 odd