“Okay, campers, rise and shine, and don't forget your booties 'cause it's cooooold out there today.” Similar to Bill Murray’s Groundhog Day, we had a winter storm blow through Michigan the day before Groundhog Day. It was bad enough for all the schools in the area to close, except, of course, Hope College. So we met and discussed the benefits of random assignment in well run experiments.
At the beginning of class, I had all the students flip a coin. I then passed out a sheet of paper and they wrote down whether they got heads or tails, their height, and their sex. I lectured for a short bit about the benefits of random assignment, mostly in the context of the Physician’s Health Study and briefly talked about blocking. Then I put the data collected in class into an applet so we could compare the distribution of heights and the distribution of sex between the heads and the tails group. It worked very well since each pair of distributions were quite similar. We then opened up an applet that simulated the same thing we just did, but could look at a distribution of the outcomes of many such random assignments.
Finally we worked on a short exploration discussing how students that write in cursive on the SAT essay scored significantly higher than those that print. The exploration also discussed an experiment where identical essays, one printed and one written in cursive, were given randomly assigned to graders. The graders tended to grade the one’s written in cursive higher.
So far this semester we have focused on a single proportion and looked at tests of significance, confidence intervals, generalizing to a population (random sampling), and now causation with random assignment. We are now ready to start inference involving two variables.
Also, like Bill Murray’s Groundhog Day, once I did this with one section of my introductory statistics course, I did in all over again with my second. “They say we’re young and we don’t know …”
Todd
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Today's Topics:
1. Happy Groundhog Day! What happened in your introductory
statistics class today? (Allan Rossman)
----------------------------------------------------------------------
Message: 1
Date: Sun, 01 Feb 2015 21:34:10 -0800
From: Allan Rossman <arossman@calpoly.edu>
To: Simulation-Based Inference <sbi@causeweb.org>
Subject: [SBI] Happy Groundhog Day! What happened in your introductory
statistics class today?
Message-ID: <54CF0C52.3010905@calpoly.edu>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Happy Groundhog Day!
I continue to find it inexplicable that neither private colleges nor
public universities see fit to cancel classes out of respect for this
august occasion. But this year I've decided to try to make the best of
this lamentable oversight, and I need your help!
I think it might be fun to ask introductory statistics teachers to
compare notes on what's happening in their classes on one particular
day. What better day than Groundhog Day for revisiting the same
question over and over, and over and over, and over and over, from
multiple perspectives?
I'm writing this after Groundhog Day has officially begun in
Punxsutawney, Pennsylvania, but it's shortly after 9pm on Super Bowl
Sunday here in California. So, to get the ball rolling on this
whimsical idea (I strongly prefer the word "whimsical" to "silly" in
this context), I'll use future tense to anticipate what will happen in
my class on Monday. I plan to be sound asleep when Punxsutawney Phil
makes his celebrated prognostication. (Too much information: Thirty
years ago I did indeed make the trek to Gobbler's Knob with my future
bride before sunrise on February 2, but I won't be up so early or
anywhere near Punxsutawney this year!)
My introductory students and I in STAT 217-09 at Cal Poly will begin the
fifth week of our ten week term on February 2 by finishing up a
discussion of principles of well-designed experiments.We?ll discuss a
study conducted at Harvard about whether students spend $50 differently
depending on whether they?re told that it?s a ?tuition rebate? or ?bonus
income.?Then we?ll consider one of the first studies of the drug AZT for
reducing mother-to-child transmission of HIV.We?ll culminate this
discussion by collecting some in-class data on a very simple randomized
experiment investigating whether grouping of letters can affect memory.
All students will receive the same 30 letters in the same order, but
some will find convenient, recognizable three-letter groupings and
others will see more irregular groupings of letters.
Then I expect to have time to introduce a study about whether swimming
with dolphins is beneficial to patients who suffer from clinical
depression. We'll discuss the design of the study and do a quick
exploration of the 2x2 table of results, setting the stage for
simulating a randomization test to assess whether the difference between
success proportions in two treatment groups is statistically
significant. Carrying out this simulation in class, using cards and
then an applet, will have to wait until February 3 when the excitement
of the momentous day has passed. (Or who knows, perhaps my students and
I will find when we awake on Tuesday that we are destined to magically
relive Monday again and again...)
Please indulge me in this fanciful exercise by replying to this
Simulation-Based Inference listserv with a description of what happened,
or will happen, in your introductory statistics class on Groundhog Day
2015. Maybe we statistics teachers will learn something interesting by
exchanging this information and reflecting on the variety of
responses.Even if not, we can honor the grand tradition of Groundhog Day
by engaging in a substantially less grand but only marginally more silly
(oops, I mean whimsical) one.
With best wishes for the special day and for an early spring (to those
of you who must endure winter),
Allan Rossman
--
Allan J. Rossman
Professor and Chair
Statistics Department
Cal Poly
San Luis Obispo, CA 93407
arossman@calpoly.edu
http://statweb.calpoly.edu/arossman/
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