I don’t really have a plan yet for today. I won’t be returning the exams (they’re graded, but I haven’t figured out what the grades mean). I’ll find out what they did with the averaging problems on the homework. If we do the GPA example and the CPI and talk about the anomalies (class size and facebook friends) I’ll be content. The latter two of these are best done with extreme examples – an interesting strategy.
Remind class that we start Excel on Thursday – in the lab.
What I did.
Worked the hw problem on contributions to the Elizabeth Warren campaign, in and out of state. The first three parts are a review of percentages and chart reading; only the last part has anything to do with weighted averages. Focussed on the qualitative predictions: since 31% of the money came from 21% of the donors (in state) their average contribution would have to be greater than the overall average. Then we checked the actual arithmetic.
Talked about where the CPI comes from – surveys, followed by weighting the increases in each category using the percentage of income spent in each category.
No one in the class game with facebook friends calculations, so I made up a fictional small social network with 100 people, one with the 99 others as friends, who themselves had no other friends. Then the average number of friends is 1.98 (just about 2) but 99% of the people have fewer friends than average! A paradox, a paradox, A most ingenious paradox.
Worked the same paradox for class size – students see a smaller value than professors.
Sadly, I did most of the talking yet again. It seems to be what the students want. Is it what they need?
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