Question

A prevalence survey conducted from January 1 through December 31, 2012, identified 1,000 cases of schizophrenia in a city of 2 million persons. The incidence rate of schizophrenia in this population is 5/100,000 persons each year. What percent of the 1,000 cases were newly diagnosed in 2012?

Answer 1

10% of 1,000 cases of schizophrenia were newly diagnosed in 2012

Explanation:

For every 100,000 people,

The incidence rate of schizophrenia = 5

There are 2,000,000 persons

2,000,000 / 100,000 = 20 * 5 = 100

So, there are 100 new cases of schizophrenia in the entire population

100 new cases / 1000 existing cases = .1 / 100

= 10%

Hence, 10% of 1,000 cases of schizophrenia were newly diagnosed in 2012.