Psychologists concerned about self-injurious behaviors (smoking, eating fatty diets, drug abuse, etc.) worry about the effects of maternal smoking on the incidence of low birthweight babies, who are known to be at risk for developmental problems. The Centers for Disease Control and Prevention has published statistics relating maternal smoking to low birthweight. The data follow in terms of the percentage of birthweights grams.

Find a way to present these data that illustrates this relationship clearly. Why is this relationship not likely to be a statistical fluke?

1989 1990 1991 1992 1993 Smokers 11.36% 11.25 11.41  11.49 11.84 Nonsmokers 6.02 6.14 6.36 6.35 6.56 Additional (and more recent) data on smoking and low birthweight can be found at http://www.smw.ch/docs/pdf200x/2005/35/smw-11122.pdf