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

[Angel626]

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.

 

[tkhunny]

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.

 

[Angel626]

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 ??