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

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.

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