pare the ratio with an F distribution on 2 and 2B degrees of freedom. Assuming that the FBI has as many as 500 estimates, the 5% critical point from an F distribution on two and 1,000 degrees of freedom is 3.005. Thus, if a given standard deviation is times larger than the pooled standard deviation for that element, one should consider remeasuring that element, in that the precision may be larger than expected by chance alone (5% of the time).


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