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Topic: Re: Exam -Reply
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Timothy Brown

Posts: 42
Registered: 12/6/04
Re: Exam -Reply
Posted: May 8, 1997 8:27 AM
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From Kevin Rees:
>AP exam questions give you FAR more information than >you need in

order to determine whether or not the student >understands the
situation of the experiment.
>Question #5 gave sample statistics for each sample and >for the
differences, about 95% of my students correctly >choose to ignore the
statistics for the differences as two >different ovens are "assumed"
to be independent (yes they >could be connected to the same power
source, be next to >each other, etc. yet without more in the question
it seems >more appropriate to treat them as independent).
>I am assuming that when the test is graded they will be >looking for
two-independent sample analysis rather than >dependent samples
analysis and will grade accordingly.

What I found most interesting about question #5 was the decrease in
% of defective chips over time in both ovens. Time is ovbiously
important, and it raises the question of whether or not the
"population" of % defective chips is normally distributed (a normal
quantile plot of Oven A's output is not particularly linear). My
initial reaction to the problem was to lean toward doing
matched-pairs on the hourly differences to eliminate the issue of
time, but I didn't think about the problem of independence. (I
haven't met with my students yet, so I don't know what they did).
How big a problem is that? Shows how much I don't know.

Tim Brown
Lawrenceville School
Lawrenceville, NJ

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