Question

In one flip of 10 unbiased coins, what is the probability of getting a result as extreme or more extreme than 8 heads?

A. .0547

B. .1094

C. .2246

D. Impossible to determine

Answer 1

The correct option is A. .0547

Explanantion:

Since the alternative hypothesis is p>0.5, more extreme values are numbers of heads closer to 10.  

The probability of 8 or more heads in 10 tosses assuming the coin is fair.  

But, the number of heads in 10 tosses of a coin assuming that the coin is fair has a binomial distribution

with n=10 and p=0.5.  
The p-value is P[8 heads] + P[9 heads] + P[10 heads].

From the binomial probability distribution,

P[8 heads]=0.044,

P[9 heads]=0.01, and P[10 heads]=0.001.  

Thus the p-value is 0.044+0.010+0.001=0.055.