Chapter 1 Psychological Science Statistical Reasoning Statistical Reasoning

Chapter 1 Psychological Science Statistical Reasoning

Statistical Reasoning 100% Percentage still functioning 99 after 10 years 98 97 96 95 Our Brand X Y Z Brand of truck

Statistical Reasoning Percentage still functioning after 10 years 100% 90 80 70 60 50 40 30 20 10 0 Our Brand X Brand Y Z Brand of truck

Statistical Reasoning § Mode § § the most frequently occurring score in a distribution Mean the arithmetic average of a distribution § obtained by adding the scores and then dividing by the number of scores § § Median the middle score in a distribution § half the scores are above it and half are below it §

Statistical Reasoning A Skewed Distribution 15 20 25 30 35 40 45 50 90 475 70 Mode Median One Family Mean Income per family in thousands of dollars 710

Statistical Reasoning § Range § § Standard Deviation § § the difference between the highest and lowest scores in a distribution a computed measure of how much scores vary around the mean Statistical Significance § a statistical statement of how likely it is that an obtained result occurred by chance

Since 9% said that Nader was the only candidate worth voting for, one would have expected to getstatistic at leastbecause 9% of the vote in There was him a biased the 2000 election. He only got from aboutthe 3%. What sample wasn't randomly drawn happened? A disproportionate number of population. Nader supporters participated in the poll in order to make him appear more viable as a candidate.

Solution: The airlines n Can we. No. conclude that had the most United, American, and complaints also had the Delta are the worst most passengers. airlines and Alaska, Southwest, and Continental are the best?

n. Solution: This clipping from USin The difference the abuse rates probably News and World stems from Report ondifferent 1/29/01 definitions for abuse in the suggests that various states. For example, Alaskans are terrible Alaska (the "worst" state) parents. Is this says that a child is true? abused if his or health or welfare is harmed or threatened. Pennsylvania (the "best" state) defines it as a recent act or failure to act.

n. Solution: No. Drunk drivers a fatality from n Can have we conclude risk 7. 66 times the while following diagram norm, non-drunk drivers a risk that have it's safer to drive only about. 6 of the while under the norm. Only a very small percentage of influence? drivers in New York City drive while under the influence, but they account for a disproportionate number of accidents.

n. Solution: The following No. As the following graph shows, the statistics suggest that reason 16 -year-olds areand safer octogenarians appear to drivers than people in be safe drivers is that they theirdrive twenties, don't nearly and as much octogenarians asthat people in other age are very safe. Is this groups. true?