I had two groups of persons, one group having 259 and another 260 individuals. the group first were treated with a medicine for a particular ailment, and 95 persons get alright i.e 36 per cent.
the second group consisting of 260 individuals was not treated with any medicine. but the persons recovered from the same ailment were 72 individuals i.e 27.6 per cent. now i had to find out the probability.