4000 women working in a factory were recruited into a study

4,000 women working in a factory were recruited into a study in 1940. Half of the women worked in manufacturing and halt in administrative offices. The incidence of bone cancer through 1970 among the 2,000 women working in manufacturing was compared with that of 2,000 women working in administrative offices. Thirty of the women in manufacturing developed bone cancer as compared to 9 of the women in administrative offices. This study is an example of a:

Solution

Case Control Study : A study that compares patient who have disease or outcome of interest with one who do not have.
In the above, we are comparing bone cancer with one those whose you have and whose you haven\'t.
In manufacturing offices, out of 2000, 30 having bone cancer while in administrative office, 9 out of 2000 having.
So, this is an example of Case- Control Study.