Solution: 2019 Fall Midterm - 15
Author: Michiel SmidQuestion
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".
(a)
1/3
(b)
1/4
(c)
1/2
(d)
1
Solution
Let’s calculate all possible combinations of the first 2 flips
- $HH$
- $HT$
- $TH$
- $TT$
Out of the 4 combinations, only 2 of them have the first flip being different from the second flip.
Therefore, the probability of the first flip being different from the second flip is $\frac{2}{4} = \frac{1}{2}$