For Questions 14-16: Use information from the table below.

The following data were collected on an early childhood intervention to prevent development of attention deficit disorders (ADD) among a group of high-risk children.The study population included 500 children attending subsidized early child education programs, of whom 250 were randomly allocated to intervention group and 250 were allocated to a control program.Children were followed for 3 years, and person-years of exposure to the intervention were totaled for the intervention and the control group.

Table 4A

Person-yrs # dvlping

exposure ADD

Intervention 630.1 9

Control 645.3 13

Calculate the measure of association for development of ADD based on exposure to the intervention.Report your answer rounded to the 100^th decimal place.