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log paper and hand calc and Reese's
Posted:
Jun 10, 1996 10:57 PM


I sent my two cents before I read all my incoming mail. Now youall will have to be patient with this old physicist while she answers the mail. As a rite of passage to the appreciation of calculators and KaleidaGraph on the Mac, I instruct my kids in the art of the hand calculation of standard deviation, the linear regression eqn and the correlation coef. (Which I taught with grave seriousness 15 years ago and used in research 30 years ago). With a set of collected data, they compare their hand calc with the calculator and with the computer. They see the factors involved and the relationships of the factors. Done once is enough. On exponentials, we use kid collected data (say radioactivity or Newton's law of cooling) and graph on semilog paper first > go to Kaleidagraph (plots loglog and semilogs). For loglog plots, we do Kepler's law concerning period vs ave distance from sun. One is power of 2 and the other power of 3, hence log log to straighten out. About the cubic and quartic and higher powers of poly. One can fit anything to a high power > and it is meaningless. This is the time for the lesson in meaning of eqn vs best fit. They must find a resource or think about physics and extrapolated values. A good one is the stopping distance of cars at various speeds (data from Georgia Drivers Manual (which they all have)). Fit to quadratic or cubic and the extrapolated distance for 100 mph is outrageous. Point made. Another outrageous extrap is from cumulated number of cases of AIDS diagnosed (downloaded from CDC webpage) . The last year shows a tad of a decrease and decrease is predicted for the future. (It is being modelled via diff eqs.; my class attended a lecture by a man currently doing this). On the reverse is TB, which was exponential decay until 1988 then the graph turns up (data from CDC by phone). The value is in the discussions of fit or not and why. Not the transformations to linear  though some of this math is important,too. In fact, I will start doing that next year  on yourall's advice. Rex  Reese's pieces are like M&Ms except peanut butter in the center instead of chocolate. Hope you have M&Ms over and under there. Reese's come in three colors while M&Ms in six (I think). All with different % occurances. Now back to grading finals  and eating M&Ms. Alice, Galloway School, Atlanta



