SE is the SD of a set of samples of a "n" number of means (fluctuating as a theoretical normal distribution) SD is used for measuring the average deviation from the mean in 1 (only one) sample. As someone else mentioned, SE and SD (1) measure different things and (2) are used for different purposes (i.e. SE for estimating intervals of confidence within which the "true" mean is). C.
Alan McLean wrote: > As is often the case, a lot of confusion arises because of vocabulary - in > particular, abbreviating. Here, we should always refer to the standard deviation OF > a specified variable, and the standard error OF a specified variable. > > 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...... > > > When to use the Standard Deviation (SD) and the Standard Error (SE)? > > 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. > > > > Voltolini > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 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 > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > "Tutto di noi � un angelo con un'ala e > possiamo volare soltanto se ci abbracciamo" > > . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
