A student takes a true-false test exam with 10 questions. If the student guesses all ten questions, find the probability he gets 7 or 8 right.
p(x=7) + p(x=8)
(.5)^7(.5)^3 + (.5)^8(.5)^2
I have the correct answers which are .117+.044= .161
But when I calculate the answer on the calculator, I get a different answer. Am I putting this into the calculator wrong?