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Topic: Re: Geometry Rubric Scoring Clarification - # 37
Replies: 7   Last Post: Jun 27, 2011 11:13 AM

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 Westendorf, Neal Posts: 235 Registered: 12/3/04
RE: Geometry Rubric Scoring Clarification - # 37
Posted: Jun 24, 2011 9:08 AM
 att1.html (12.2 K)

We worked on finding the points of intersection with the calculator. We
used the graphing tools as well as the table where the y values
coincided. This issue points out what I stressed with my kids-that
graphing by hand is only as good as your ruler or your curve sketching
ability. It falls short very quickly when dealing with curves or
problems using 'real' values for slopes and intercepts. It was quite
unreasonable to expect students to get an exact value of .5 when
sketching a parabola. The key should have included something like
'accept reasonable answers'. I didn't correct that question but would
have been very tempted to allow .7 if the students curve crossed a bit
above the middle of that line. I certainly would have accepted it in
class if they were required to do the problem by hand.

Neal

From: owner-nyshsmath@mathforum.org
[mailto:owner-nyshsmath@mathforum.org] On Behalf Of Amy Sacca
Sent: Friday, June 24, 2011 8:41 AM
To: nyshsmath@mathforum.org
Subject: Re: Geometry Rubric Scoring Clarification - # 37

told me that "Students should be able to see that the parabola and line
intersect at exactly half way between the lines, and should always check
their answers anyway. Even still, they have a graphing calculator with
the capabilities to use that to calculate the point of intersection."

Amy

>>> <TKENYON@crcs.wnyric.org> 6/24/2011 8:33 AM >>>

Oh, and the parabola line intersection - I never in a million years
expected non-integer values. We had a lot of students ignore the point
of intersection that wasn't a "nice" point. I'm not 100% sure how the
students actually would be expected to find the intersection
graphically, particularly since points of intersection can have
irrational values. Using a table of values is not graphically. And
although it's a "graphing calculator", using the button to find the
point of intersection is not "finding it graphically" either. Although,
apparently, in the future I'll have students use the calculator to
calculate the point of intersection, then just pretend they found it
graphically. We had a student guess that the x-value was -.7 instead of
-.5, because that's about where it intersected on her graph. That was
a 99%.

-Tom Kenyon
CRCS Mathematics/Physics
tkenyon@crcs.wnyric.org

-----owner-nyshsmath@mathforum.org wrote: -----

To: nyshsmath@mathforum.org
From: TKENYON@crcs.wnyric.org
Sent by: owner-nyshsmath@mathforum.org
Date: 06/24/2011 07:48AM
Subject: Re: Geometry Rubric Scoring Clarification - # 37

The only thing that bummed me out about the geometry was the
problem with the measures of 3 arcs given as a ratio. To solve for the
arcs, we'd see 12x=360, x=30. Then, quite a few students filled in the
diagram with the correct arc measures - 150, 120, 90 degrees, and then
wrote down "30 degrees" for the answer. Even though the arithmetic is
trivially simple for many students, since they didn't write down
(150-90)/2, our grading team only gave 2 points, because "how do we know
they didn't think the angle was just x." I don't know if I had more
than 1 student not have 30 degrees for the answer, but many lost 2
points for not showing that work. The rubric states that 150, 90,
120, but no further correct work = 2 points. I tried calling and
calling and calling state ed, but the line was always busy. Grades were
due, we had to make a decision. *sigh*. 1 student shy of 50% mastery
though, so I was relatively happy with my results.

-Tom Kenyon
CRCS Mathematics/Physics
tkenyon@crcs.wnyric.org

-----owner-nyshsmath@mathforum.org wrote: -----

To: nyshsmath@mathforum.org
From: "loretta boyce"
Sent by: owner-nyshsmath@mathforum.org
Date: 06/24/2011 07:21AM
Subject: Re: Geometry Rubric Scoring Clarification - #
37

The linear quadratic system question: if they listed
one point OR the other without work they receive 0 credit. If they
listed both points of intersection without work, they receive 1 credit.

Loretta

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Date Subject Author
6/23/11 Guest
6/24/11 loretta boyce
6/24/11 Tom Kenyon
6/24/11 Tom Kenyon
6/24/11 Amy Sacca
6/24/11 Westendorf, Neal
6/24/11 Eleanor Pupko
6/27/11 jlitt