Question

Andy claims that his bird can do single-digit multiplication. He shows the bird 12 cards with simple multiplication problems that are either correct or incorrect. The bird correctly identifies the correctness of the card 9 times out of 12. If the bird were simply guessing, how many would the bird be expected to get correct?

3

Answer 1

the bird would be expected to get 9 right

Answer 2

Explanation:

Given that Andy claims that his bird can do single-digit multiplication. He shows the bird 12 cards with simple multiplication problems that are either correct or incorrect. The bird correctly identifies the correctness of the card 9 times out of 12.

If the bird simply guesses the probaility of correctness =p = 9/12 = 3/4

n = no of trials =12

Since each trial is independent of the other, the distribution of X, the correct answers is binomial

Hence mean = expected value of correct answers =np

=12(3/4) =9