# Important information about Marginal & Conditional Probability

See attached file for table.

Which Probability formula should be used? Please explain.

A researcher wants to prove the efficacy of three drugs to treat headaches. Results are given in the following table. If one of these subjects is randomly selected:

12- Find the probability that the subject had a headache given that the subject was treated with Aleve answers : A) 0.56 B) 0.47 C) 0.74 D) 0.64

is this P( A |B) probability that event A occurs given that event B has occurred already

or P( B |A) probability that event B occurs given that event A has occurred already

Please explain in detail

13- Find the probability that the subject had no headache or was treated with Tylenol: answers A) 0.18 B) 0.52 C) 0.81 D) 0.33

Is this P(A U B) = P(A) + P(B) - P(A n B)

Please explain

14- Find the probability of getting someone who was NOT treated with Aleve

answers A) 0.80 B) 0.58 C) 0.54 D) 0.94

#### Solution Summary

The solution provides step by step method for the calculation of probabilities and conditional probabilities. Formula for the calculation and Interpretations of the results are also included.