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.
