This was “Day 15” (start of week 5) in my intro stat course for math/stat/econ majors. We just finished Ch. 1 of ISCAM and I handed back exams today. So they had seen the statistical investigation process, but all in terms of one categorical variable, and today we were going to start comparing two groups. I started by asking them to raise their hand if they watched the superbowl and then to raise their hands for male/female, and asked whether I could now use that data to investigate whether males were more likely to have watched than females. This seemed to generate some reasonable discussion that led to the need for conditional proportions. So then we did an example of hearing loss levels among teens “now” (2005-6) vs. a few years ago (early 90s) from NHANES data. (The speculation that heavier use of ear buds is causing problems.) We went through the basics of two-way tables, difference in conditional proportions, segmented bar graphs with these data. Then in this class we have them simulate taking independent random samples from two binomial processes with the same probability of success, generate a null distribution for the difference in sample proportions, and then review/introduce the p-value as a way to measure how unusual the statistic is. Tomorrow we move on to the two-sample z-test.
HGD,
Beth
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. RossmanProfessor and ChairStatistics DepartmentCal PolySan Luis Obispo, CA 93407arossman@calpoly.eduhttp://statweb.calpoly.edu/arossman/
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