SIG on Teaching Statistics using R

Example(s) of Biomodal distributions

Dear R users:

I am currently teaching a course in Statistics. Can someone give an R code(s) to create a biomodal curve(s)
with shaded area of 90% and with 5% in each tail

With many thanks
abou

 

==========================
AbouEl-Makarim Aboueissa, Ph.D.
Associate Professor of Statistics
Graduate Program Coordinator
Department of Mathematics & Statistics
University of Southern Maine
96 Falmouth Street
P.O. Box 9300
Portland, ME 04104-9300
USA

Tel: (207) 228-8389
Fax: (207) 780-5607
Email: aaboueissa <at> usm.maine.edu
          aboueiss <at> yahoo.com

Office: 301C Payson Smith

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Bob | 7 Jan 18:18

R for absolute beginners


>From time to time I have posted a link to the materials on R that I
developed for my online courses.  Their only claim to fame is that
they are way below the level of all the R documentation I have seen
and so suited for very non-technical beginners (I hope). There have
been a variety of problems with that link, including things being
invisible so you do not even know they are (not) there.  So I have put
a cosmetically challenged version on my own website.  There may still
be problems, but at least now I have access and can fix them!  Let me
know if you find any.  There should be several pages on R Commander
and several on plain R.  I think several more are still missing and I
will continue to hunt for them.

     http://statland.org/R/Rstart.html

------->  First-time AP Stats. teacher?  Help is on the way! See
http://courses.ncssm.edu/math/Stat_Inst/Stats2007/Bob%20Hayden/Relief.html
      _
     | |          Robert W. Hayden
     | |          142 Main Street
    /  |          Apartment 104
   |   |          Jaffrey, New Hampshire 03452  USA
   |   |          email: bob@ the site below
  /    |          website: http://statland.org
 | .   y          phone: (603) 532-7224 (home)
 ''''''

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Paul Johnson | 22 Nov 21:19

Regression textbooks

What regression textbooks are you using in stat courses that introduce
regression?  I'm looking for something with approximately the same
intended scope as Cohen, Cohen, West and Aiken, Applied Multiple
Regression.  That presents OLS, interactions, categorical variables,
and elementary GLM (logit, poisson).    In our second regression
course, we work in more detail with John Fox's Applied Regression and
the Companion book.  Leading up to that, I need some book that is a
bit more applied in nature, with examples from various fields of
study. Something about 200 pages long that ends with a chapter on
logistic regression would be fine.  There was a book called Regression
Analysis By Example, by Samprit Chatterjee, Ali S. Hadi and Bertram
Price, was headed in the right direction, but it seems not to be in
development any more.

If it has R example code for certain basic analysis, it would be perfect.

Suggestions?

--

-- 
Paul E. Johnson
Professor, Political Science
1541 Lilac Lane, Room 504
University of Kansas

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Ali Zanaty | 30 Oct 14:31

Comparing two Regression Lines (Clarify)


Dear All R users:

I am teaching a statistical class. Can someone help me to write an R code to
compare two regression lines.
More specific:
(1) Test the equality of slopes.

and 

(2) Test the equality of Y-intercepts (elevations). 

Please use this example of data.

Data for line 1:

============

 

X1<-c(25, 50, 100, 200, 400)

Y1<-c(77.7, 78, 64.3, 59.7, 51.2)

 

 

Data for line 2:

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Ali Zanaty | 30 Oct 13:28

Comparing two regression lines


Dear All R users:

I am teaching a statistical class. Can someone help me to write an R code to
compare two regression lines. 

More specific, test the equality of slopes and
Y-intercepts (elevations). Please use this example of data.

Data for line 1:

============

 

X1<-c(25, 50, 100, 200, 400)

Y1<-c(77.7, 78, 64.3, 59.7, 51.2)

 

 

Data for line 2:

============

 

X2<-c(25, 50, 100, 200)

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Randall Pruim | 9 Jul 21:26

Re: Plotting the p-value


I just joined this list, and I see in the archives that there have  
been several answers to this already, but I'll add another one:

 > install.packages(mosaic)

 > example(xpnorm)

xpnorm() is a function that behaves much like pnorm() but provides  
more verbose output and a plot to go with the lower "tail"  
probability.  If you run in RStudio, the last example will add a  
slider.  A fancier version of this will likely be available soon with  
a manipulate=TRUE option.

The plot is a bit crude at the moment and looks better in some window  
sizes than in others.  I happy to receive suggestions for  
improvement.   The current version of mosaic on CRAN is a beta  
release.  A new version should be there in a few days and we are  
working to have as stable, robust, and comprehensive a package as we  
can muster ready my JSM.

There are other x-functions in the package as well (xhistogram(),  
xchisq.test, etc.) that add extra features to the plain-vanilla  
functions without the initial x.

There are a number of other things in this package (and in the works)  
to aid in teaching statistics.  Perhaps in a future post we can say  
more about other things we are working on.  Watch for new between now  
and JSM or catch one of us there.

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Manoj Aravind | 6 Jul 09:19

Odds Ratio for evaluating Diagnostic tests

Hi friends,

I have a doubt reg the application of odds ratio.
When evaluating a diagnostic test, what odds ratio I should apply?
When I use..
*>oddsratio (X)** *
the OR I get is not ad/bc.

Thank you.

Regards,
Dr Manoj Aravind,
PG Resident,
Dept of Community Medicine,
Osmania Medical College,
Hyderabad, India.

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Wayne Gray | 2 Jul 21:12

ANOVA questions

Greetings.

I am not totally sure where to post this query so forgive me if this is the wrong SIG. However, I do teach stats
in conjunction with experimental design and the question is one that is of considerable interest right
now to several of my grad students and myself - hence this presents a weak rationale for sending the query to
this listserv.

As background, I am very familiar with Type III marginal SS for ANOVAs. However, we have a situation where a
reviewer is insisting on an analysis that requires thin slicing our data so that we do not have
observations in some of the cells for some of our Ss. I think I understand what R is telling me, but I am not
positive that I do. Even worse, I don't know how to explain the analysis (assuming I have interpreted it
correctly) to the editor or to the readers of the journal who, like me, are familiar with Type III ANOVAs.

I have tried to attach the R file plus the data file to this email. I am not sure whether the listserv will allow
attachments. If not these files can be found here:

Rcode: files.me.com/graywayne/7z7db3
data: files.me.com/graywayne/688878

What I think is the "takeaway" point is that there is no evidence in our data that the factor "dens.targ" is
significant or that any of its interactions are significant. Given that the other analyses strongly
support our interpretation of the results, I would like to conclude that any effect of density of the
target stimuli on response time is very weak at best. This is a very satisfactory conclusion to me,
however, I want to go the extra mile to show the editor that we tested this as best we could. Although it might
appear in the paper, it is not clear that it would. It may be the sort of thing you do to present to the Editor
but leave out of the final version of the paper.

Any help, comments, pointers, etc will be much appreciated.

BTW: This is a visual search paradigm where the factor of interest is the density of distractors in the

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Matt Curcio | 29 Jun 19:48

Lists of R packages

Greetings All,
I would like to find out which R packages I have on my machine and
transfer that set of packages to a new machine.  I have investigated
the command 'installed.packages' and got a partial list but this is
not comprehensive. (!?!)  The partial list does not include the
libraries that I do not normally load on start-up.
Any suggestions?

Conversely, once I have found the complete list can I use
'install.package' to batch install all the packages to another
computer?
Cheers,
M

--

-- 

Matt Curcio
M: 401-316-5358
E: matt.curcio.ri <at> gmail.com

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Francis Smart | 26 Jun 05:00

Message displayed when opening RData file

Hello,

I am wondering if there is any way to display a message automatically when a
workspace is restored and to have that message saved as part of the
workspace.

I would like R to say after
[Previously saved workspace restored]

To see data input >data in the console
To see data variable descriptions input >desc in the console

Thank you for your help,
Francis

--

-- 
Francis Smart
--------------------
PhD Student - Michigan State University
Agricultural, Food, and Resource Economics (AFRE)
Measurement and Quantitative Methods (MQM)

Cell: (406) 223-8108

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Ali Zanaty | 5 Jun 15:23

help is needed

Dear All R users:

I am teaching a statistical class. Can someone help me to create the attached 
graph in R. I have other graphs, but once I know how to create this one, I will 
be able to do other ones.

With many thanks
Ali

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