Message-ID: <f8e6ff050903301529u20c2e480n4bce9d83c429a1ab@mail.gmail.com>
Date: 2009-03-30T22:29:23Z
From: Hadley Wickham
Subject: I need your thoughts on teaching with R
In-Reply-To: <40e66e0b0903301412i275524d1g4df1e9925f2b3915@mail.gmail.com>
> What do I mean by simplify? ?There are many topics in an introductory
> statistics course that are ingrained in the curriculum but really are
> there for the sake of approximation or computational simplification.
> How many introductory texts still describe how to approximate a
> "difficult" distribution by a "simpler" distribution (hypergeometric
> by binomial, binomial by Poisson or Gaussian, etc.)? ?When you can
> calculate the exact probability why do you want to waste time teaching
> an approximation and rules like "when np > 5 ..."? ?Even a basic
Even knowing how to look up numbers in a table is an outdated skill!
> graphical presentation, the histogram, is outmoded. ?The purpose of
> the histogram is to give us a picture of the density. ?Why not use a
> density plot for this? ?There is a great advantage in that you can
> easily overlay density plots from different groups, not to mention the
> fact that it shows a smooth approximation to the density. ?In the past
> we used histograms because it was comparatively simple to choose bins
> and count the observations in the bins then produce a bar chart. ?We
> can do better than that now.
I agree 100% with your points apart from this one. I'm not a big fan
of density estimates because most real-life distributions are not
smooth, continuous and unbounded, like most density estimators assume
they are. It's also much harder to understand how a density plot is
made, and while I don't think students need to understand the
motivations and theory for every tool they use, I think they should
understand how their basic graphic tools work. A happy intermediate
is the frequency polygon, which has more favourable theoretical
properties than the histogram, but is equally easy to understand (and
you can overlay them like densities)
> I have over the years produced slides for classes based first on
> Devore's books then on Peter's book and now on the Cohen and Cohen
> book. ?I am willing to make these available, including the source
> code, so others can borrow code or presentation approaches if they
> wish. ?I am not familiar with open documentation licenses like
> Creative Commons. ?If it would help to stimulate discussion I will
> make them available without copyright. ?I would be particularly
> interested in corresponding with potential text book authors on some
> of the techniques that I think can be used to simplify presentation of
> R code and graphics. ?I don't have plans to embark on writing a text
> myself.
I would love to see these!
Hadley
--
http://had.co.nz/