Question

3. [10 Points) Consider an exam with 28 multiple choice questions. Assume that each question has three solution choices but only one of them is correct. A student who didn't study for the exam is going to make a guess. a. What is the probability that he guesses only 15 questions correctly? b. What is the probability that he guesses at least 15 questions correctly? c. What is the probability that he guesses more than 10 and less than 15 questions correctly? d. How many questions do you expect him to guess incorrectly?
please answer part B and C

Answer 1

9 Toth Here Here n = 28 is z 10 17 12 lange, so we can approximati Binomial distributh with Mimp = 28 X = 9.33 6:22, 0 = 2:49 (b) P(x > 15) =P ( X-9:33 ), 19-9.33) = P(7) 2. 28) =l- P(Z < 2.98 09. mpli-p) = 28*yzx% 2:49 2:49 3 I - 0.9887 = 0.0113 4 O P( 10 < x <15) PL 10-9.3% 5X-.9.23 { 15,-9.33) 2.49 2.49 2:49 p(0.27 37 < 2.28) $12.98 $10.97) ? 0.9887 - 0.6064 0.3823 -