In the situation which you are presumably referring to, you have some random variable measured on individual members of a population, and are calculating sample means. In this case, the standard deviation of the variable measures the variation of the variable over the members of the population.
Your sample means are values of a different variable! This variable is measured on members of the population of simple random samples of specified size selected from the population of individuals. The standard error (of the sample means) measures the variation of the variable 'sample mean' over the population of samples.
Both your 'SD' and your 'SE' are standard deviations. The difference between them is the difference between the variables they refer to.
Cheers.
Alan
On Wednesday, April 2, 2003, at 12:19 AM, VOLTOLINI wrote:
Hi, my doubt is simple......
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When to use the Standard Deviation�(SD) and the Standard Error (SE)?
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I preffer to use the SE because when comparing groups of data the box plots with SE give me the same results as the tests. Then, it seems that using a box plot with SE the conclusion is more powerfull.
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Voltolini
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Prof. J. C. VOLTOLINI
Grupo de Estudos em Ecologia de Mamiferos (ECOMAM)
Universidade de Taubate, Departamento de Biologia
Praca Marcelino Monteiro 63, Bom Conselho.
Taubate, SP. CEP 12030-010. BRASIL.
Tel: 0XX12 - 2254165 (Lab. Zool.) ou 2254277 (Depto. Biol.)
E-Mail: [EMAIL PROTECTED]
http://www.ecomam.hpg.ig.com.br
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"Tutto di noi � un angelo con un'ala e
possiamo volare soltanto se ci abbracciamo"
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