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The previous calculation used an approximation which was only valid in cases where the means being compared were similar; this resulted in very odd claims being made, e.g. that 0 +/- 0 is a difference of -100% +/- 1% from 100 +/- 1. The new calculation scales sample standard deviations by the means, and yields approximately correct percentage difference bounds providing that the reference population is bounded away from zero. (In the case where the values being compared are not sufficiently bounded away from zero, the distribution of ratios becomes much harder to calculate, and is not likely to be useful anyway.) Note that when ministat is used for its intended purpose of determining whether two samples are statistically different, this change is unlikely to have any noticeable effect; in such cases the means will be similar enough that the correction applied here will be minimal.
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