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Topic: Rounding...and other exam details
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Barrier, Robert

Posts: 12
Registered: 12/6/04
Rounding...and other exam details
Posted: Jan 14, 1997 11:10 AM
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Hello Larry, Chris, and all...

I've enjoyed reading all of the postings on the list, and find it reassuring
that these discussions are taking place; especially, it's nice to know that
I'm not the only one with questions.

This is my second posting (I accidentally sent a blank message--sorry) and I
would like to start by saying that I have no qualifications for writing...I'm
a third year teacher, with only two college prob/stat courses under my belt
(but maybe over my head). I did teach a non-AP course using IPS for my
first two years. The only thing I feel I have to offer this forum is an eye
for details, particularly of the logistical nature.

To that end:

The College Board's Advanced Placement Course Description--Statistics (the
"Acorn Book") is an essential guide to teaching this course. It is my
opinion that anyone teaching the course _MUST_ have a copy. All of the
formulas and tables that the students can expect to be given are printed in
this they will appear on the exam.

There is also a draft version of the Teacher's Guide which explains the
scoring of the open-ended questions and investigative task. A rubric is
given, along with sample problems with student work and explanations of how
the rubric was applied.

The teacher's guide gives the following instructions with regard to rounding
answers and use of symbols:

> "Remind your students that on the exam they should not round numbers at
> intermediate steps in a calculation. Answers should be rounded only at the
> end and then not too much. For example, a z-score should be rounded to two
> decimal places in order to use the table, but each step in the calculation
> should not be rounded at all or the final z-score may be quite different
> from what it would have been otherwise.

> A rule that is usually satisfactory is to round the final answer to one
> more decimal place than was given in the data."

> "Students should define all symbols when writing solutions to open-ended
> questions. For example, when writing a null hypothesis, a student should
> not write just
> mu = 75,
> but should define what mu represents. A clear and complete statement of a
> null hypothesis would be:
> mu = 75, where mu is the mean of the reading
> test scores for all students in this school.
> If students practice this policy throughout the course, they will have less
> trouble understanding that the null hypothesis is about the population, not
> about the sample."

It might be helpful to show our students how easy it is to use the memory
capabilities of our calculators, not only for ensuring accuracy, but also for
conserving keystrokes. The fewer strokes, the fewer opportunities for
careless error.

By the way, for more information about obtaining copies of any College Board
publications for the AP program, call AP Order Fulfillment @ (609) 771-7243.
I haven't looked, but there is probably a way to get info online at

Hope this helps...



Bob Barrier
C. E. Jordan High School
6806 Garrett Road
Durham, NC 27707

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