00:01
A fair quarter is flipped three times.
00:04
For each of the following probabilities, use the formula for the binomial distribution and a calculator to compute the requested probability.
00:13
Okay, so a fair coin has a probability of 50 -50, so our proportion is 0 .5.
00:20
We're going to flip this coin three times, so n equals three.
00:25
So for part a, we're finding the probability of getting three heads.
00:32
So we have three combination three times 0 .5 to the third power.
00:40
And that is 0 .125.
00:44
For part b, we're finding the probability of getting exactly two heads.
00:48
This time it'll be three combination two times 0 .5.
00:53
Since we have the same price of 50 -50 probability, i don't need to split them up and say 0 .5 to the second power times 0 .5 to the first power.
01:01
I can just say 0 .5 to the third power.
01:03
And that's going to give me 0 .375.
01:09
For part c, the probability of getting at least two heads, so the probability of two or more heads, that would be getting two or three heads, which we already calculated the probability of up above, so i can just add 0 .125 plus 0 .375 together, and i get a probability of 0 .5...