Re: [Phys-l] explanatory and response variables (was calibration )

[Hugh Haskell <hhaskell@mindspring.com>]

At 23:35  -0400 8/8/07, Ken Fox wrote:
> Egad! I had no idea of how confused my students must have been as I blithely
> discussed that the independent variable should be on the x or horizontal
> axis and the dependent on the y or vertical axis.

So what do you tell your students when they do an experiment where 
they put photogates at fixed positions along, say, a tilted air 
track, and measure the times that the glider passes them. Have they 
not done an experiment where the independent variable is distance and 
the dependent variable is time? And if so what do you tell them when 
they plot time on the y-axis and distance on the horizontal, and find 
that the velocity measurements come out in sec/m?

Why worry about dependent and independent at all? If they are not in 
a position to figure out for themselves what the optimum way to plot 
a graph is, then just tell them put whichever variable will be the 
numerator of slope measurements on the y-axis and the other one on 
the x-axis. And when they complain that their chemistry teacher told 
them to worry about dependent and independent variables, just tell 
them that you are freeing them from that restriction. All they have 
to do now is to think about what they are going to do and do the 
thing that makes most sense. That means about a million arbitrary 
rules that they no longer have to worry about.

Then you can take up a collection among your faculty colleagues to 
provide help for the chemistry teacher who just had a nervous 
breakdown, because now his most righteous rules 
(dependent/independent variables and significant figures--see earlier 
posts) have both been violated.

Hugh
--

************************************************************
Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

(919) 467-7610

Hard work often pays off after time. But Laziness always pays off now.

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