Ever since the discovery of germs, parents have been telling their children to wash their hands. Common sense tells us that this should help minimize the spread of infectious diseases and lead to better health. A study reported in the University of California at Berkeley Wellness Letter (volume 13, issue 6, March 1997) may confirm the advice our parents gave us. A study in Michigan tracked a random sample of children, some of whom washed their hands four or more times during the school day. The number of sick days from colds and flu and the number of sick days from stomach illness were recorded for the past year. Column 1 contains a code representing whether the child washed his or her hands four or more times per school day (1) or not (2). Column 2 stores the number of sick days from cold and flu and column 3 contains the number of sick days from stomach illness.

a. Do these data allow us to infer that a child who washed his or her hands four or more times during the school day will have fewer sick days from cold and flu than other children?

b. Repeat Part (a) for sick days from stomach illness.