Answer:
a. 12 / 50 = 0.24 or 24%; b. 21 / 50 = 0.42 or 42%
Explanation:
1. to find the estimated probability that it will take at least 5 patients to find who it isn't effective on, count the outcomes of EEEE. this means that it was effective on 4 patients, therefore requiring a 5th patient to find the noneffective person.
a. 12 / 50 = 0.24 or 24%
2. to find the estimated probability that it will be effective on exactly 3/4, look for boxes with 3 E's and 1 N (in any order)
b. 21 / 50 = 0.42 or 42%
hope this helps :)