5 raisins per cookie (r = 5), or 500 per batch of doughExplanation
This way of stating the cookie problem is due to Feller. We have the requirement that p(0) = 0.0100. The easy way to get the answer is to scan along the top or p(0) line of the Poisson Table, to find the smallest value of r for which the value of p(0) is 0.0100 or less. This turns out to be r = 5, for which p(0) = 0.0067. At this level of raisins, a raisinless cookie will turn up only every 150 cookies. The first batch of 100 cookies seems moderately well protected.
On the other hand, suppose you bake a second batch? Suppose you are running a home business making refrigerator cookies? Suppose your middleman, the guy in the frozen food truck, holds out to you a partly sliced roll of frozen cookie dough and says, "Mrs Beauregard found that her third cookie from this roll had no raisins at all in it." What then?
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24 Aug 2007 / Contact The Project / Exit to Statistics Page