An ACME University researcher studies the effects of sleep d…
An ACME University researcher studies the effects of sleep deprivation on math exam grades. She randomly subjects 200 of 400 volunteers to intermittent loud noises while sleeping. The remaining volunteers were left alone. This went on for three days, after which the subjects took a standard mathematics exam. The counts are recorded in the frequency table below. Treatment\Grade A B C D F Row Totals Sleep-Deprived 10 50 80 30 30 200 Not Sleep-Deprived 30 70 50 40 10 200 What is the probability that one of the 400 volunteers chosen at random was sleep-deprived and scored a B or better?