Mathematics 1228A/B Final: fmLEC20
8 Oct 2019
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Lecture 20 (Mar1)
Warmup: Allan is a fan of Arsenal FC. If the club wins tonight’s football game, there is a 90% chance Allan will go to the pub to
celebrate with a drink. If Arsenal loses there is a 20% chance Allan will drown his sorrows with a drink at the pub. The chance of
Arsenal winning is 70%. If later I see Allan having a drink, what is the probability Arsenal lost?
Ex. Determine Pr[𝑋𝑀].
Ex. At Western students major in Science, Arts, Business or Medicine. 30% of students are in science, 20% are in arts, 40% are in
business and the remaining 10% are majoring in medicine. A new scholarship has come out! If a student in science applies, they have
a 50% chance of getting the scholarship, and if someone in arts applies they have a 90% chance. An applying business student has a
60% chance to earn the scholarship, while the medical student has a 70% chance. At a reception banquet a student who won the
scholarship is randomly selected, what is the probability they are a student in science.
2.7 Independent Trials
A lot of experiments are repeated over and over.
Some experiments are done hundreds of thousands of times to ensure accuracy. To motivate our eventual formulas let us consider a
simple example:
Ex. Suppose we have an unfair coin (60% - H, 40% - T). We’ll flip it three times. What are the chances I flip exactly two heads?
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MATH 1228A/B Full Course Notes
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