I would think that a negative value for a statistic that takes on non-negative values would be suspiciously low. But some people think I'm overly skeptical.
There may or may not be a discussion of this in one or more of the links in 'Spreadsheet Addiction'. http://www.burns-stat.com/pages/Tutor/spreadsheet_addiction.html The executive summary is, "Don't do statistics in spreadsheets, especially Excel." Patrick Burns [EMAIL PROTECTED] +44 (0)20 8525 0696 http://www.burns-stat.com (home of S Poetry and "A Guide for the Unwilling S User") Lance Westerhoff wrote: >Hello All- > >I found an inconsistency between the R-squared reported in Excel vs. >that in R, and I am wondering which (if any) may be correct and if >this is a known issue. While it certainly wouldn't surprise me if >Excel is just flat out wrong, I just want to make sure since the R- >squared reported in R seems surprisingly high. Please let me know if >this is the wrong list. Thanks! > >To begin, I have a set of data points in which the y is the >experimental number and x is the predicted value. The Excel- >generated graph (complete with R^2 and trend line) is provided at >this link if you want to take a look: > >http://www.quantumbioinc.com/downloads/public/excel.png > >As you can see, the R-squared that is reported by Excel is -0.1005. >Now when I bring the same data into R, I get an R-square of +0.9331 >(see below). Being that I am new to R and semi-new to stats, is >there a difference between "multiple R-squared" and R-squared that >perhaps I am simply interpreting this wrong, or is this a known >inconsistency between the two applications? If so, which is >correct? Any insight would be greatly appreciated! > > >====================== > > > # note: a is experimental and c is predicted > > summary(lm(a~c-1)) > >Call: >lm(formula = a ~ c - 1) > >Residuals: > Min 1Q Median 3Q Max >-2987.6 -1126.6 -181.7 855.3 5602.8 > >Coefficients: > Estimate Std. Error t value Pr(>|t|) >c 0.99999 0.01402 71.33 <2e-16 *** >--- >Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 > >Residual standard error: 1423 on 365 degrees of freedom >Multiple R-Squared: 0.9331, Adjusted R-squared: 0.9329 >F-statistic: 5088 on 1 and 365 DF, p-value: < 2.2e-16 > > > version > _ >platform powerpc-apple-darwin7.9.0 >arch powerpc >os darwin7.9.0 >system powerpc, darwin7.9.0 >status >major 2 >minor 2.1 >year 2005 >month 12 >day 20 >svn rev 36812 >language R > >====================== > > >Thank you very much for your time! > >-Lance >____________________ >Lance M. Westerhoff, Ph.D. >General Manager >QuantumBio Inc. > >WWW: http://www.quantumbioinc.com >Email: [EMAIL PROTECTED] > > >"Safety is not the most important thing. I know this sounds like heresy, >but it is a truth that must be embraced in order to do exploration. >The most important thing is to actually go." ~ James Cameron > >______________________________________________ >[email protected] mailing list >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > > > > > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
