Question 7

In the table shown below, please find the number of cases of disease A and the mid-year population counties X and Y. What was the age-adjusted incidence rate for disease A in county Y per 1,000 person-years? Please use the total population of both county X and county Y as standard (0.545 for under 18 years and 0.455 18+) and write the answer as rate per 1,000 person-years to one decimal place.

	County X			County Y
Age group	No. of persons	No. of cases of disease A	Incidence per 1,000	No. of persons	No. of cases of disease A	Incidence per 1,000
<18 years old	1,000	5	5.0	5,000	25	5.0
18 years old	3,000	90	30.0	2,000	60	30.0
Total	4,000	95	23.8	7,000	85	12.1