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Law of total probabilities
Archie is taking a course in probability
theory. Discussion sessions with the
class TA (teaching assistant) conflict
with Archie's trips to the beach. Archie
has to decide between attending TA
sessions, which might help him do better
in the probability course, and going to
the beach. Archie learns that
% of
past students who did not attend TA
sessions received a grade of B or below
in the course. Archie also learns that
% of past students received a grade
higher than B. After some thought,
Archie decides to attend the TA
sessions. Not all of his classmates share
his decision; in fact, only
out of every
of his classmates attend discussion
sessions with the TA. Compute the
probability that Archie will receive a
grade higher than a B in the course.
Round your answer to two decimal
places.
(If necessary, consult a
list of formulas
.)
We'll examine the information in the above paragraph.
We'll write
for the event "achieves a grade higher than a B." We
are told that the probability of this event is
. We'll write
for the event "meets in
discussion sessions with the TA," and we'll write
for the
complementary
event.
We are told that
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 Spring '08
 Staff

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