Question

Statistics question

Walmart claims that their checkout scanners correctly price 98.9% of the items sold. How many items would you expect to buy, on average, to find one that scans incorrectly? Round your answer up to the next integer
a) 2
b) 91
c) 99
d) 500
e) 989

Answer 1

(b) 91

Explanation:

The probability of an item scanning correctly is 98.9%, so the probability of an item scanning incorrectly is 1 - 98.9% = 1.1%.

The expected number of items to buy to find one that scans incorrectly is 1 / 1.1% = 91. This means that you would expect to buy 91 items on average to find one that scans incorrectly.

Rounding up to the next integer, the answer is 92. Therefore, the correct answer is (b) 91.