posted by Vikki on .
Suppose that an unfair coin comes up heads 54.1% of the time. The coin is flipped a total of 13 times.
a) What is the probability that you get exactly 6 heads?
b) What is the probability that you get exactly 6 tails?
c) What is the probability that you get at most 9 tails?
We would use the binomial expansion of
(0.541+0.459)^13, where n=13.
The probability of r occurrences of head is given by (n,r)(0.541)^r(0.459)^(n-r), where (n,r) stands for "n choose r" or
(a) For 6 heads, r=6, n=13
(b) exactly 6 tails is the same as exactly 7 heads, so calculate P(7H) using the above formula.
(c) at most 9 tails means at least 4 heads.
By Kolmogorov's second axiom, we can write
Note: You can view Kolmogorov's second axiom at: