# Re: [R] Is this correct?

From: Daniel Malter <daniel_at_umd.edu>
Date: Mon, 24 Nov 2008 02:35:34 -0500

Bill is right. Generally, a more appropriate type of question to the list would, for example, be: I want to run OLS. What is the function to do it in R (although this is a particularly stupid example as it is on the first pages of almost all manuals)? You would typically write to the R list if you want to get a certain thing done and can't get it done (assuming that it is not homework!). The main difference to your question being that you already know what the "thing" is (which, in your case, is your modeling question).

Therefore your question is generally not one that anybody here should answer. You as the researcher determine which relationships are of interest and which make sense. You should consult the tutor/TA of your class if you have any questions what the relationships of interest are. S/he is getting paid to help you. Go there and say: Here are my ideas...what do you think? Second, if you are required to do this in R, they should give you materials to learn R from, respectively they should teach you R. Further, there are numerous sources/manuals out there from which to learn the basics of R. And they are free as R is. Just google them.

Cheers,
Daniel

cuncta stricte discussurus

-----Ursprüngliche Nachricht-----
Von: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] Im Auftrag von Rlover
Gesendet: Sunday, November 23, 2008 9:46 PM An: r-help_at_r-project.org
Betreff: [R] Is this correct?

A researcher was interested in whether people taking part in sports at university made more money after graduating, taking into account the students' GPA. They sampled 200 alumni from a large university. The variables are: income (income 10 years after graduating), sports (1 if they did sports, 0 if they did not), and GPA (the grade point average at university). Discuss the relationship between taking part in sports, GPA, and income for these data.

The R code I used so far is

Does sports predict GPA?

> lm1<-lm(GPA~sports)
> summary(lm1)

Does sports predict income?
> lm2<-lm(income~sports)
> summary(lm2)

Does GPA predict income?
> lm3<-lm(income~GPA)
> summary(lm3)

Does sports predict income after accounting for GPA?
> lm4<-lm(income~GPA+sports)
> summary(lm4)

Can someone let me know is the above is correct? I am not sure if to keep all four regressions or only 1 and 4. Also, I need to plot the data on a graph or table. Can anyone suggest how to do this? Thank you in advance :)

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