Special Note: Sometimes epidemiologists want to calculate the incidence rate of some outcome, however measurement of person-time is not possible, or the assumption of an equal risk to outcome throughout time is not met. In such instances, we can use the mid-year population (i.e. population on July 1) as the denominator. This type of incidence rate is comparable to a person-time rate.

1.In Carson City, 150 new cases of Disease X were diagnosed among women aged 30-39 between January 1, 1981 and December 31, 1981. The mid-year population for this demographic in Carson City was 10,000.What is an estimate for the incidence rate of Disease X among women aged 30-39 in that time?

Prevalence

2.Examination of a 10% sample drawn from a total of 20,000 state government employees revealed 50 people with clinical evidence of coronary heart disease.

a.What is the prevalence of coronary heart disease in the sample population?

b.Would these 50 people be included in a study of the incidence of coronary heart disease in the above sample population?Why or why not?

3.Between January 1, 2015 and December 31, 2015 there were 25 cases of renal failure in a nursing home with a resident population of 200. On March 1, 2015 there were 7 cases of active renal failure.

a.What is the point prevalence of renal failure on March 1, 2015?

b.What is the period prevalence of renal failure for 2015?