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Date:         Tue, 23 Feb 1999 18:11:29 -0300
Reply-To:     "Hector E. Maletta" <hmaletta@OVERNET.COM.AR>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@UGA.CC.UGA.EDU>
From:         "Hector E. Maletta" <hmaletta@OVERNET.COM.AR>
Subject:      Re: Coefficient of Variation
Comments: To: shailendra@CANADA.COM
Content-Type: text/plain; charset=us-ascii

Its the ratio of standard deviation to the mean. More than 'precision' it reflects the relative dispersion of data around the mean. Besides, in a normal distribution 95% of the cases lie within 1.96 standard deviations around the mean, thus if the coefficient is, say, 0.15, and the distribution is normal, then about 95% of the cases will lie in the interval delimited by (1-0.30)*mean and (1+0.30)*mean. Many psychological, medical and biological variables are known or expected to have a nearly normal distribution of frequencies, and thus this concept may be handy. Sociological and economic variables, though, have usually non-normal distributions.

All this, of course, is not to be confused with the distribution of sampling errors, which is always expected to be normal if the samples are randomly selected and of sufficient size. The standard deviation of the sampling distribution (variability among many hypothetical samples of the same size) is usually estimated as the standard deviation observed in your sample, divided by the square root of the sample size. But in this context the notion of a coefficient of variation, though feasible, is not commonly used.

Hector Maletta Universidad del Salvador Buenos Aires, Argentina

shailendra@CANADA.COM wrote: > > Recently I came across a term called coefficient of variation, which measures the precision of the estimated data. > > My curiosity how important it is know the coefficient of variation in survey analysis, how it is calculated at the sample level, and is there any % bench-mark for accepting data for analysis. > > Any reference or comments are thankfully welcome. > > -------------------------------------------------------------------- > Get free personalized email from Canada.com at http://www.ehmail.com


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