Displaying 2 results from an estimated 2 matches for "wonnacott".
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wannacott
2009 Jan 27
3
How to compare two regression line slopes
...ents
> fit2 <- lm(y~x, df2)
> s2 <- summary(fit2)$coefficients
> db <- (s2[2,1]-s1[2,1])
> sd <- sqrt(s2[2,2]^2+s1[2,2]^2)
> df <- (fit1$df.residual+fit2$df.residual)
> td <- db/sd
> 2*pt(-abs(td), df)
[1] 0.9510506
However, I also found a procedure in Wonnacott & Wonnacott, that is
based on the use of a mute variable D that will have a binary value
according to the group to which a given point belongs (group : D=0;
group 2: D=1). Then the equation that is computed is as follow:
y = b0 + b1.x + D.b2.x
which can be computed in R with:
> fit &...
2005 Sep 12
5
remedial stats education
In short:
I didn't take enough stats courses in college. Now I am working on scientific
research and I feel somewhat lost when it comes to designing the statistical
framework. I have looked through the books at:
http://www.r-project.org/doc/bib/R-books.html
I even tried to read [17] Julian J. Faraway. Linear Models with R. This book
is too advanced. It helped a little bit but I still