Participants in a study of a new medication a or a placebo. find p (placebo and improvement). you may find it to make a tree diagram of the problem. of all those who participated in the study, 80%received medication a. of those who received medication a, 76% reported an improvement. of those who received the placebo, 62%reported no improvement.

The tree diagram is constructed and attached as an image below.

80% of the participants received medication, this means 20% received placebo. Among those who received medication, 76% reported improvement, this means rest 24% reported no improvement. Among those who received Placebo, 62% reported no improvement, this means rest 38% reported improvement.

The probability of P(Placebo and Improvement) will be = 20% x 38%
P(Placebo and Improvement) = 0.20 x 0.38 = 0.076 = 7.6%

This means there is 7.6% probability that those who received Placebo reported Improvement.