Every time I try I get the wrong answer...
What is the minimum # of responses needed from a survey of 20 cities to guarantee that at least 15 responses will be from one of the 20 cities?
What is the minimum # of responses needed from a survey of 20 cities to guarantee that at least 15 responses will be from one of the 20 cities?
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14*20 + 1 = 281
Suppose we took 280 samples and by miraculous coincidence we happen to get exactly 14 responses from every city. If this didn't happen we would already have >14 from at least one city. If we managed to do this, the moment we took the 281st sample we would have to have 15 samples from one of the cities.
Suppose we took 280 samples and by miraculous coincidence we happen to get exactly 14 responses from every city. If this didn't happen we would already have >14 from at least one city. If we managed to do this, the moment we took the 281st sample we would have to have 15 samples from one of the cities.