TABLE 4-2
An alcohol awareness task force at a Big-Ten university sampled 200 students after the midterm to ask them whether they went bar hopping the weekend before the midterm or spent the weekend studying, and whether they did well or poorly on the midterm. The following result was obtained.

-Referring to Table 4-2, what is the probability that a randomly selected student did well on the midterm or went bar hopping the weekend before the midterm?
A) 30/200 or 15%
B) (80+30)/200 or 55%
C) (30+70)/200 or 50%
D) (80+30+70)/200 or (110+100-30)/200 or 90%

Question

TABLE 4-2
An alcohol awareness task force at a Big-Ten university sampled 200 students after the midterm to ask them whether they went bar hopping the weekend before the midterm or spent the weekend studying, and whether they did well or poorly on the midterm. The following result was obtained.
 
-Referring to Table 4-2, what is the probability that a randomly selected student did well on the midterm or went bar hopping the weekend before the midterm?
A) 30/200 or 15% 
B) (80+30)/200 or 55% 
C) (30+70)/200 or 50% 
D) (80+30+70)/200 or (110+100-30)/200 or 90%

Quizplus · Accepted Answer

The question asks for the probability that a student did well on the midterm or went bar hopping, which includes students who did both. Therefore, we add the percentages in the overlapping section (30%) to the percentages in each individual section (80% for did well, 70% for went bar hopping) to get (80+30+70)/200 or (110+100-30)/200, which simplifies to 90%. Therefore, the best choice is D.

TABLE 4-2 An Alcohol Awareness Task Force at a Big-Ten University Sampled