Answer: 0.04395
Explanation:
Given: 10 true-false questions.
So, we will have 50% chances (probability = 0.5) of being correct.
Prob( Exactly 80% score) = Prob (exactly 8 answers correct)
As we observe, if X= number of correct answers, then X~ Binomial (n=10, p=0.5)
So, Prob( Exactly 80% score) = Prob (exactly 8 answers correct)
=[tex]\binom{10}{8}\times(1/2)^{8}}\times(1/2)^{2}[/tex]
= 0.0439453125
= 0.04395
