Statistics Homework Questions

Question

 In a multiple choice exam, there are 4 questions and 4 choices for each question (a, b, c, d). Nancy has not studied for the exam at all and decides to randomly guess the answers. What is the probability that:
(please round all answers to four decimal places)

a) the first question she gets right is question number 3?

b) she gets all of the questions right?

c) she gets at least one question right?

Answer 1

a.  P(wrong wrong, right in 1st three answers) = (¾)²(¼)

 

b. P(all 4 are right) = (¼)²

 

c. P(not all wrong) = 1 - (¾)⁴ = 0.6836