(w + r)^20 ... p(wrong) = p(right) = 0.5
the 11th term is ... 20C10 w^10 r^10 = 0.1762
... the answer is the sum of the 1st ten terms
the total probability (sum of all terms) is 1
half of the "center" term is ... 0.0881
sum of the 1st ten terms is ... 0.5 - 0.0881
You will need a binomial table for n = 20 for this problem. Suppose that a quiz consists of 20 True-False questions. A student hasn't studied for the exam and will just randomly guesses at all answers (with True and False equally likely). What is the probability that the student will get less than 10 right?
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