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Assume a database with 10,000 elements of data is queried, through a statistical interface, for the average data value. The response is determined using the random-sample query method, with a subset of 500 elements being used. Assuming you had access to all data elements, how could you determine what the least accurate response could be?

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closed as off-topic by bobthechemist, Kuba, RunnyKine, Yves Klett, Sjoerd C. de Vries May 13 '14 at 20:39

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This question appears to be off-topic. –  Sektor May 13 '14 at 15:16

1 Answer 1

You can take a sample of random selections and determine the probability of an inaccurate result.

In the example below a 'response' (e.g. mean) of less than -0.0767 or greater than 0.0767 has a small 0.27% chance of occurring.

See: 68–95–99.7 rule

elements = RandomReal[{-1, 1}, 10000];
selections = Table[RandomSample[elements, 500], {10000}];
means = Mean /@ selections;
sd = StandardDeviation[means];
 Epilog -> {Line[{{-3 sd, 0}, {-3 sd, 400}}], Line[{{3 sd, 0}, {3 sd, 400}}]}]

enter image description here

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