Binomial Q: A test consists of 10 true-or-false questions...

A test consists of 10 true/false questions. To pass the test a student must answer at least 8 questions correctly.

a. If a student guesses on each question, what is the probability that the student will pass the test

b. Find the mean and standard deviation of number of questions answered correctly.

Pr(at least 8) = Pr(8) + Pr(9) + Pr(10)

Pr(10) = 1*(0.5^0)*(0.5^10)

Pr(9) = 10*(0.5^1)*(0.5^9)

This should be ringing some bells.

the probability of P(10)= 1(0.5^0) (0.5^10)
P(10)=9.7656 ?

P(9)= 10(0.5^1) (0.5^10)
P(9)= .009765625 ??