Solution: 2016 Fall Midterm - 15

Author: Michiel Smid

Question

You flip a fair coin 9 times. Define the event

A = "the result of the first flip is not equal to the result of the second flip".

What is $\Pr(A)$?

(a)

(b)

1/2

(c)

1/4

(d)

1/3

We can write down all the possibilities for the first 2 flips.

There are 4 total possibilities. There are 2 possibilities where the first 2 flips are not equal.

Thus, $ Pr(A) = \frac{2}{4} = \frac{1}{2} $