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Re: [Phys-l] Independent Variables



On 10/30/2006 11:00 PM, thecraftyphantom@australia.edu wrote:
The syllabus that I teach states,

"A student: justifies the appropriateness of a particular investigation
plan:

11.2 plan first-hand investigations to:
a) demonstrate the use of the terms ‘dependent‘ and ‘independent‘ to
describe variables involved in the investigation
b) identify variables that needed to be kept constant, develop strategies
to ensure that these variables are kept constant,
and demonstrate the use of a control"

I have no clear idea what that means. Are the independent variables
supposed to be kept constant? Are the dependent variables supposed
to be kept constant?

Are we using feedback loops to hold certain variables constant?
-- If not, how can a variable be a constant?
-- If so, isn't that unnecessarily complicated for an introductory
lesson?

I've planned and carried out more than a few "investigations". The
ideas of "dependent" and "independent" are too simple to be useful;
they don't cover all the cases, and they don't express the important
issues in experiment design. Sometimes tiny changes in the mode of
operation of the apparatus can change a so-called independent variable
into a dependent variable.

Similarly, there are about 10 different things that "control" could
mean ... some important, some not, some suitable for introductory
classes, some not.

Can you give some specific examples, i.e. scenarios where students
are supposed to be able to identify independent and dependent
variables????

Despite using some examples and discussing "cause and effect",

Cause and effect is an important topic. What does the /physics/
syllabus say about this? Which laws of physics address the issue
of cause and effect? Most attempts to impute cause-and-effect to
introductory laws of mechanics are fallacious.
http://www.av8n.com/physics/causation.htm

It is highly likely that these concepts will be tested in some form or
other and so I have some concern about whether my students can meet the
syllabus requirements. The wording of the syllabus also means that I
cannot use substitute terminology except as an explanatory note, as the
students will be tested using the syllabus language. The final examination
is a state test that I have no control over.

Does the rest of the syllabus look like the passage quoted above?

If so, you should gather the villagers, get some torches and pitchforks,
and march on the state offices.

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