Variance

[jdent]

Variance is the standard deviation squared. But the equztion is it over n-1 or just n. I thought that it was n-1 as I saw in a math text book. BUt in a question I think from the ADA web site they do it as n. Any imput?

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[Streetwolf]

IIRC n-1 is the sample st dev and n is the population. I usually use n-1. They should both give you pretty close answers unless there aren't as many data points.

I know time is a factor but start with n-1 and if it doesn't give you a listed answer either choose the closest answer (if the choices are spaced apart pretty well) or try with just n and see if you get an exact answer.

 

[jdent]

Thanks!