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Binomial Calculators and TAR

This blog has previously discussed Catalyst's TAR for Smart People on the night of October 5, 2015, and noted on the night of November 13, 2015, its recommendation to use the Raosoft Calculator to determine the sample size needed for predictive coding. John Tredennick's guide also recommends using a Binomial Calculator to estimate the confidence interval for how accurate the percentage of relevant documents found in a sample set will be in showing the actual number of relevant documents. So if you have a sample set of 1000 documents, and you find 50 relevant documents, and the complete document set is 2,000,000, you're dealing with a richness level of apparently 5 per cent, and extrapolating that supposed percentage to the full set, we come up with an exact guess (a point estimate) that there are 100,000 relevant documents in the total population. The binomial calculator lets us set a confidence interval of a likely range in which the actual number of relevant documents will fall.

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