Question
Suppose that you flip a coin 11 times. What is the probability that you achieve at least 4 tails?
Answers
Sky Parker
same name
and it 6
and it 6
R_scott
this is a binomial probability
... p(h) = p(t) = .5
(h + t)^11 = h^11 + 11 h^10 t + 55 h^9 t^2 + 165 h^8 t^3 ...
p(at least 4 tails) is 1 minus the sum of the 1st four terms of the expansion
... 1 - [.5^11 * (1 + 11 + 55 + 165)] = .887
... p(h) = p(t) = .5
(h + t)^11 = h^11 + 11 h^10 t + 55 h^9 t^2 + 165 h^8 t^3 ...
p(at least 4 tails) is 1 minus the sum of the 1st four terms of the expansion
... 1 - [.5^11 * (1 + 11 + 55 + 165)] = .887