AP Statistics

 How plausible is H 0 ? ◦ Depending on H 0 plausibility, you may choose a smaller alpha. ◦ If H 0 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.”

 If rejecting H 0 would ◦ costs lots of money ◦ possibly cost lives ◦ costs jobs  then alpha is usually very small  Example: Global Warming

 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?

 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.

 Read 10.3  Problems 10 #59-62 and 64, 65