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From another bully HS teacher
Date: 2011, March 20, 16:06:34 PDTlist junk cut
To: PTSOS@yahoogroups.com
Subject: [PTSOS] Re: Significant Figures (and units too!)
Reply-To: PTSOS@yahoogroups.com
I think repeated exposure and habit-formation is the key. Model best practices and communicate that the students are expected to emulate. Deploy carrots and sticks as necessary. Sorry if it sounds authoritarian or top-down, it's just that the clock is ticking and there are rainbows (or transfer orbits) to get to. I doc them peanuts for misuse/neglect of units more so than sig figs. (If I pose a paper/pencil question re the power involved in 3 amps at 6 volts, I'm more OK with an answer of "18 watts" than I am with an answer of "20".) If their sloth is a greater priority than their grade, they will not succumb to my operant conditioning. Otherwise, they will.
Trust me, I'm more OCD than most. I get a bee in my bonnet over leading zeros! As far as I'm concerned, there is no numerical value that begins with a point. So 0.5 kg good; .5 kg bad. I once challenged students to find me published examples of numerical values between -1 and +1 that omitted the leading zero. Not finding any examples in their math or science books, they ran to their math teachers who are apparently lax and lazy about leading zeros. Thus was produced a CRC Handbook from the '50s with trig tables. Since sine and cosine values range from -1 to +1, the leading zeros were omitted. Not sure why they wanted to go against the grain of every textbook they ever used with students (and The Chicago Manual of Style--yes, I checked) in favor of sloppiness, but they certainly curried favor with the children on that one.
Again, BF Skinner's diabolical methods can work wonders in these situations.