Answer:
6
Step-by-step explanation:
probability of answering a question correct p=1/4
let minimum number number of question that would be unusual =n
hence from binomial distribution P(X>=n) <0.05
[tex]\sum_{x=n}^{11}\binom{11}{x}(1/4)^{x}(3/4)^{11-x} <0.05[/tex]
by solving:
n=6
it would be unusual to get 6 or more questions correct by guessing alone.