For the Parental HIV data produce a scatterplot of the age at which adolescents first started smoking versus the age at which they first started drinking alcohol. Based on the graph, do adolescents...

For the Parental HIV data produce a scatterplot of the age at which adolescents first started smoking versus the age at which they first started drinking alcohol. Based on the graph, do adolescents tend to start smoking before drinking alcohol, or vice versa? Calculate the correlation coefficient. Exclude all adolescents who had not started smoking or had not started drinking alcohol by the time they were interviewed.