The GOOD and FUN first day !
Hi,I am a biologist and new to teachingStats for undergraduate Biology students in a Brazilian University. I'd like to start off with something new in the first day class !!! The idea is toget the studentsattention for aGOOD and FUN world of thinking and avoid the idea that numbers are boring, not easy,not useful for biologists interested incells, animals and plants and not in "math"... !!! Please send me what your suggestions !!! (this is not being easy with biologists.) Thanks Voltolini _Prof. J. C. VoltoliniGrupo de Estudos em Ecologia de Mamiferos - ECOMAMUniversidade de Taubate - Depto. BiologiaPraca Marcellino Monteiro 63, Bom Conselho,Taubate, SP - BRASIL. 12030-010TEL: 0XX12-2254165 (lab.), 2254277 (depto.)FAX: 0XX12-2322947E-Mail: [EMAIL PROTECTED]
Re: One more time--Two Factor Kruskal-Wallis
Hi, Carol. I'm taking the liberty of posting this to the Edstat (statistical education) list as well as the Minitab list. On Fri, 21 Sep 2001, Carol DiGiorgio wrote: My question is: I would like to run 2-way ANOVA on my data. Unfortunately it doesn't meet the assumptions of normality or homogeneity of variance. I've worked with the data to find a transformation, but have been unable to find one. 1. Which assumption of normality? The only one that comes close to being _required_ is the assumption that the _residuals_ from the model are normally distributed. (I ask, because it seems often to be believed that the raw variable itself, infected by possible effects of the design factors, should be normally distributed; this is not the case.) 2. How badly unequal are you cell variances? Unless they vary by at least an order of magnitude, unequal variances won't much affect your conclusions, and if your cell, n's are equal (or if not, if the cells with the larger variances have the larger n's), the size of the test (that is, the empirical P-level) will be not far from the nominal value. 3. Unequal variances will affect the sensitivity of post hoc comparisons, however. I want to run a non-parametric 2-way ANOVA using Minitab, and determine whether the factors or the interaction are significant (I'm guessing a 2 factor Kruskal-Wallis, but I don't know what tests exist). If any of the factors were significant I would like to run a non-parametric multiple comparison test to determine where there are significant differences. Is it possible to do this in Minitab (or any other statistical program)? If I were doing it, I'd run an ordinary two-way ANOVA, using either TWOWAY or ANOVA; or, if the design were unbalanced, using GLM (since neither TWOWAY nor ANOVA will handle unbalanced data). Then inspect the pattern(s) among the means, probably displaying them graphically, with an eye toward possible useful interpretations. If I were really concerned that the unequal variances might represent something real in the population of interest (rather than an inconvenience of sampling, in this particular sample), I'd convert the dependent variable to ranks (in another column of the worksheet!) and repeat the two-way analysis on the ranks. This would give you the equivalent of a two-way Kruskal-Wallis, or a Friedman, test. YOu haven't described your data well enough for me to tell whether a Friedman test is appropriate (see FRIEDMAN in the MINITAB Reference Manual). If it is not, you can ALWAYS simulate a two-way analysis in the framework of a one-way analysis by identifying each cell separately: e.g., a 3x4 two-way ANOVA can be analyzed as a one-way ANOVA with 12 levels. (This would apply to KRUSKAL-WALLIS (q.v.) as well as to ONEWAY.) You just have to be clever, afterwards, in defining the particular contrasts (or sets of contrasts) that identify what a two-way analysis would have reported as main effects and interactions -- but, again, that's just a matter of displaying the cell means (or medians) in the form of a two-way layout. Thank you in advance. Carol HTH.-- DFB. Donald F. Burrill [EMAIL PROTECTED] 184 Nashua Road, Bedford, NH 03110 603-471-7128 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: definition of metric as a noun
In article 9ogurt$d79tc$[EMAIL PROTECTED], Neville X. Elliven [EMAIL PROTECTED] wrote: Herman Rubin wrote: The OED cites the following use of metric as a noun: 1921 Proc. R. Soc. A. XCIX. 104 In the non-Euclidean geometry of Riemann, the metric is defined by certain quantities . . A good example of bad usage: *what* metric, *what* quantities? The reader should not be left hanging with those questions unanswered. This is not bad usage at all. In mathematics, the word metric as a noun refers to a general type of distance, not necessarily the type in common use. It is certainly bad usage, for the following reason: the phrase, the metric, implies that there is *one* metric function on Riemannian geometry, which is false. This reason has nothing to do with distance measure in general, as commonly understood, or otherwise. It is not bad usage, because a PARTICULAR Riemannian geometry is given by a particular metric; in fact, by the local quadratic form defining the differential metric. -- This address is for information only. I do not claim that these views are those of the Statistics Department or of Purdue University. Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399 [EMAIL PROTECTED] Phone: (765)494-6054 FAX: (765)494-0558 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Free program to generate random samples
Jon Cryer wrote: I wouldn't call bootstrapping sampling from a population. Would you? Actually, yes. The population defined by the original sample. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Free program to generate random samples
Jerry Dallal wrote: I wouldn't call bootstrapping sampling from a population. Would you? Actually, yes. The population defined by the original sample. More precisely: sampling with replacement from the original sample... Greets Diego Kuonen -- Diego DOT Kuonen AT epfl DOT ch diego AT kuonen DOT com http://stat.kuonen.com http://www.Statoo.com `If you can imagine it, you can achieve it; if you can dream it, you can become it.' Powered by Open Source! = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: definition of metric as a noun
The phrase 'the metric' is being used here to signify the type of its class. This is perfectly ordinary usage, with no implication that there is only one member of the class. E.g. The pen is mightier than the sword. On Sat, 22 Sep 2001 03:09:55 GMT, [EMAIL PROTECTED] (Neville X. Elliven) wrote: Herman Rubin wrote: The OED cites the following use of metric as a noun: 1921 Proc. R. Soc. A. XCIX. 104 In the non-Euclidean geometry of Riemann, the metric is defined by certain quantities . . A good example of bad usage: *what* metric, *what* quantities? The reader should not be left hanging with those questions unanswered. This is not bad usage at all. In mathematics, the word metric as a noun refers to a general type of distance, not necessarily the type in common use. It is certainly bad usage, for the following reason: the phrase, the metric, implies that there is *one* metric function on Riemannian geometry, which is false. This reason has nothing to do with distance measure in general, as commonly understood, or otherwise. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Free program to generate random samples
Diego Kuonen wrote: Jerry Dallal wrote: I wouldn't call bootstrapping sampling from a population. Would you? Actually, yes. The population defined by the original sample. More precisely: sampling with replacement from the original sample... Well, yes, but since my original comment had a smiley attached, I wasn't attempting to be rigorous here. In any case, contrary to the poster's comment that prompted my first response, in general it would not be bad statistics to sample with replacement. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
