Question

Suppose that you flip a coin 12 times. What is the probability that you achieve at least 6 tails

Answer 1

Ans:

Use binomial distribution with n=12 and p=0.5

P(x=k)=12C_k*0.5^k*(1-0.5)^12-k

x	P(x)
0	0.0002
1	0.0029
2	0.0161
3	0.0537
4	0.1208
5	0.1934
6	0.2256
7	0.1934
8	0.1208
9	0.0537
10	0.0161
11	0.0029
12	0.0002

P(x>=6)=1-P(x<=5)

=1-BINOMDIST(5,12,0.5,TRUE)

=0.6128