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Q&A #5103

Teachers' Lounge Discussion: Grading policy

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From: RON <rselby@cinci.rr.com>
To: Teacher2Teacher Public Discussion
Date: 2003072912:02:32
Subject: Re: Math Teacher responds

On 2003072720:24:12, Anonymous wrote:
>Hi there Claudia,
>
>I read with interest your method for figuring out grades.
>I got very excited at first thinking you had found a simpler
>way to figure grades.  But, being a math teacher, I had to test
>your method.  If you average the grades first, and then average the
>averages, you get a much different grade than your method. 
>
>Here's an example:
>
>Your method:  60/100  + 17/20  + 8/10  = 85/130  = 65%
>
>My method:      .60   +  .85   + .80   = 2.25/3  = 75%
>
>
>What do you think?
>
>Anonymous
>California
>

The question which needs to be answered is why are different
assignments or tests given different possible point values? If the
intent is to give more weight to certain assignments or tests , then
the method of averaging the averages defeats the purpose. If the
assignments and tests are all supposed to be equally weighted , then a
simpler method of grading would be to assign the same number of points
possible to all assignments and tests. (Some instructors use 100 as
the basis for all assignments and tests. Some use another number.)

The reason for the lower final average in the first example given is
due to the fact that the student scored poorly on the most heavily
weighted assignment. 

As an example from the "real world" , let's look at a baseball
player's batting average. Suppose he gets 30 hits in his first 100 at
bats of the season. His average for that period would be 30/100 or
.300. For the next 20 at bats he gets 10 hits. His average for this
period would be 10/20 or .500. In order to calculate his current
batting average for the season, the correct calculation would be 40
hits out of 120 at bats or 40/120 or .333. If the average of the
averages is used , then 
(.300 + .500)/2 = .400 which is incorrect.

RON

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