thank you Dr. Iasonas Lamprianou
Assistant Professor (Educational Research and Evaluation) Department of Education Sciences European University-Cyprus P.O. Box 22006 1516 Nicosia Cyprus Tel.: +357-22-713178 Fax: +357-22-590539 Honorary Research Fellow Department of Education The University of Manchester Oxford Road, Manchester M13 9PL, UK Tel. 0044 161 275 3485 iasonas.lampria...@manchester.ac.uk --- On Tue, 30/3/10, William Revelle <li...@revelle.net> wrote: > From: William Revelle <li...@revelle.net> > Subject: Re: [R] error bars > To: "Iasonas Lamprianou" <lampria...@yahoo.com>, r-help@r-project.org > Date: Tuesday, 30 March, 2010, 13:56 > Iasonas, > > In response to PS.1 > try error.bars in the psych package. > > Bill > > > > At 1:04 AM -0700 3/30/10, Iasonas Lamprianou wrote: > >Dear friends, > >I have a statistical question. Sometimes, if I compare > boys to girls > >on a specific variable, the error bars (confidence > interval of > >means) seem to overlap slightly. Still, when I run a > t-test, I find > >statistically significant differences. The rule is > clear: if the > >confidence intervals do not overlap, then there is > statistically > >significant difference. But if they overlap slightly, > we have to use > >a t-test to know for sure if the the two means differ > significantly. > >The point is: is there a rule of thumb to say, for > example, "if the > >overlap is less than 20% of the length of the standard > error, then a > >t-test would give significant results?" > > > >thank you for your time > > > >P.S.1 is there an easy way to plot error bars in R? > >P.S.2 an interesting discussion about this - highly > recommended to > >read it - can be found at > >http://scienceblogs.com/cognitivedaily/2007/03/ill_bet_you_dont_understand_er.php > > > >jason > > > >Dr. Iasonas Lamprianou > > > > > >Assistant Professor (Educational Research and > Evaluation) > >Department of Education Sciences > >European University-Cyprus > >P.O. Box 22006 > >1516 Nicosia > >Cyprus > >Tel.: +357-22-713178 > >Fax: +357-22-590539 > > > > > >Honorary Research Fellow > >Department of Education > >The University of Manchester > >Oxford Road, Manchester M13 9PL, UK > >Tel. 0044 161 275 3485 > >iasonas.lampria...@manchester.ac.uk > > > > > > > > > > > > > >______________________________________________ > >R-help@r-project.org > mailing list > >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. > > > -- > William Revelle > http://revelle.net/revelle.html > 2815 Lakeside Court > http://revelle.net/lakeside > Evanston, Illinois > It is 6 minutes to midnight http://www.thebulletin.org > ______________________________________________ R-help@r-project.org mailing list 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.