> On Dec 2, 2016, at 6:16 AM, Ashim Kapoor <ashimkap...@gmail.com> wrote: > > Dear Pikal, > > All levels except the interactions are compared to the Intercept. I'm a > little confused as to what's going on in interaction terms eg. the cell > wool B : tension M. It's mean is : > 28.78 and 28.78 - 44.56 = -15.78 != 21.111. > > It's something like 44.56 (intercept) -16.333 (wool B) -.20.556 (tension > M) + 21.111 (woolB:tensionM) = 28.782. > > I don't know how to sum up the above line in terms of differences > succinctly.
The aov estimate will not exactly equal the observed mean (this is _statistics_ after all). You should be comparing the mean of that cell to the estimate: 44.556 + (-16.33) +(-20.556) + (21.11) The difference between the observed mean and the estimated mean is known as a 'residual' and the squared sum of the all residuals is what this being minimized ... over all the cells including the one implicitly associated with the Intercept. This isn't really on-topic for Rhelp since you are not having difficulty in getting the R program to perform its duties, but are rather in need of statistical education. That not what this mailing list is set up for. -- David. > >> >>> -----Original Message----- >>> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Ashim >>> Kapoor >>> Sent: Thursday, December 1, 2016 2:48 PM >>> To: r-help@r-project.org >>> Subject: [R] Interpreting summary.lm for a 2 factor anova >>> >>> Dear all, >>> >>> Here is a small example : - >>> >>>> model <- aov(breaks ~ wool * tension, data = warpbreaks) >>>> summary.lm(model) >>> >>> Call: >>> aov(formula = breaks ~ wool * tension, data = warpbreaks) >>> >>> Residuals: >>> Min 1Q Median 3Q Max >>> -19.5556 -6.8889 -0.6667 7.1944 25.4444 >>> >>> Coefficients: >>> Estimate Std. Error t value Pr(>|t|) >>> (Intercept) 44.556 3.647 12.218 2.43e-16 *** >>> woolB -16.333 5.157 -3.167 0.002677 ** >>> tensionM -20.556 5.157 -3.986 0.000228 *** >>> tensionH -20.000 5.157 -3.878 0.000320 *** >>> woolB:tensionM 21.111 7.294 2.895 0.005698 ** >>> woolB:tensionH 10.556 7.294 1.447 0.154327 >>> --- >>> Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 >>> >>> Residual standard error: 10.94 on 48 degrees of freedom >>> Multiple R-squared: 0.3778, Adjusted R-squared: 0.3129 >>> F-statistic: 5.828 on 5 and 48 DF, p-value: 0.0002772 >>> >>>> model.tables(model,"e") >>> Tables of effects >>> >>> wool >>> wool >>> A B >>> 2.8889 -2.8889 >>> >>> tension >>> tension >>> L M H >>> 8.241 -1.759 -6.481 >>> >>> wool:tension >>> tension >>> wool L M H >>> A 5.278 -5.278 0.000 >>> B -5.278 5.278 0.000 >>> >>> >>>> model.tables(model,"m") >>> Tables of means >>> Grand mean >>> >>> 28.14815 >>> >>> wool >>> wool >>> A B >>> 31.037 25.259 >>> >>> tension >>> tension >>> L M H >>> 36.39 26.39 21.67 >>> >>> wool:tension >>> tension >>> wool L M H >>> A 44.56 24.00 24.56 >>> B 28.22 28.78 18.78 >>>> >>> >>> I don't follow the output of summary.lm. I understand the output of >>> model.tables for effects and means. For instance what does 44.556 >>> represent ? Is it the grand average ? The grand mean is 28.14815. Can >>> someone help me understand the output of summary.lm ? >>> >>> Best Regards, >>> Ashim >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>> https://stat.ethz.ch/mailman/listinfo/r-help >>> PLEASE do read the posting guide http://www.R-project.org/posting- >>> guide.html >>> and provide commented, minimal, self-contained, reproducible code. >> >> ________________________________ >> Tento e-mail a jakékoliv k němu připojené dokumenty jsou důvěrné a jsou >> určeny pouze jeho adresátům. >> Jestliže jste obdržel(a) tento e-mail omylem, informujte laskavě >> neprodleně jeho odesílatele. Obsah tohoto emailu i s přílohami a jeho kopie >> vymažte ze svého systému. >> Nejste-li zamýšleným adresátem tohoto emailu, nejste oprávněni tento email >> jakkoliv užívat, rozšiřovat, kopírovat či zveřejňovat. >> Odesílatel e-mailu neodpovídá za eventuální škodu způsobenou modifikacemi >> či zpožděním přenosu e-mailu. >> >> V případě, že je tento e-mail součástí obchodního jednání: >> - vyhrazuje si odesílatel právo ukončit kdykoliv jednání o uzavření >> smlouvy, a to z jakéhokoliv důvodu i bez uvedení důvodu. >> - a obsahuje-li nabídku, je adresát oprávněn nabídku bezodkladně přijmout; >> Odesílatel tohoto e-mailu (nabídky) vylučuje přijetí nabídky ze strany >> příjemce s dodatkem či odchylkou. >> - trvá odesílatel na tom, že příslušná smlouva je uzavřena teprve >> výslovným dosažením shody na všech jejích náležitostech. >> - odesílatel tohoto emailu informuje, že není oprávněn uzavírat za >> společnost žádné smlouvy s výjimkou případů, kdy k tomu byl písemně zmocněn >> nebo písemně pověřen a takové pověření nebo plná moc byly adresátovi tohoto >> emailu případně osobě, kterou adresát zastupuje, předloženy nebo jejich >> existence je adresátovi či osobě jím zastoupené známá. >> >> This e-mail and any documents attached to it may be confidential and are >> intended only for its intended recipients. >> If you received this e-mail by mistake, please immediately inform its >> sender. Delete the contents of this e-mail with all attachments and its >> copies from your system. >> If you are not the intended recipient of this e-mail, you are not >> authorized to use, disseminate, copy or disclose this e-mail in any manner. >> The sender of this e-mail shall not be liable for any possible damage >> caused by modifications of the e-mail or by delay with transfer of the >> email. >> >> In case that this e-mail forms part of business dealings: >> - the sender reserves the right to end negotiations about entering into a >> contract in any time, for any reason, and without stating any reasoning. >> - if the e-mail contains an offer, the recipient is entitled to >> immediately accept such offer; The sender of this e-mail (offer) excludes >> any acceptance of the offer on the part of the recipient containing any >> amendment or variation. >> - the sender insists on that the respective contract is concluded only >> upon an express mutual agreement on all its aspects. >> - the sender of this e-mail informs that he/she is not authorized to enter >> into any contracts on behalf of the company except for cases in which >> he/she is expressly authorized to do so in writing, and such authorization >> or power of attorney is submitted to the recipient or the person >> represented by the recipient, or the existence of such authorization is >> known to the recipient of the person represented by the recipient. >> > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
