one thought is this ...
the easier the question ... the less likely you will find big differences
... so, you might want to concentrate your "efforts" on items more in the
midrange of difficulty or harder ones
At 03:05 PM 1/22/01 -0500, Lee Creighton wrote:
>I have some data to analyze for my dissertation, but I'm not sure what
>method to use to answer the question I am investigating. This may not be the
>correct newsgroup for it, but there are rumors that some statisticians read
>it.
>
>First, the data set is from the Third International Mathematics and Science
>Study, and consists of (among other things) a student's imputed mathematics
>ability score, the region of the US where this student lives, as well as the
>response to each question on the test. There were about 15 forms of the test
>given, so each student didn't answer each question.
>
>In other words, I have something like this:
>
>MathScore Region Question 1 Question 2 ... Question n
>100 NorthEast correct incorrect ... correct
>130 Central incorrect incorrect ... correct
>115 NorthEast incorrect correct ... incorrect
>. . . . .
>. . . . .
>. . . . .
>112 South correct incorrect ... correct
>
>The dataset consists of about 6000 students, but there is a fair amount of
>missing data.
>
>Using a simple ANOVA, I have found that there is significant difference of
>scores between regions of the country. What I'd like to do now is
>investigate WHICH questions differentiate among regions. For example,
>suppose question 1 really differentiates between the Northeast and the rest
>of the country, i.e. people in the northeast tended to get the question
>correct while the rest of the country didn't. This would perhaps tell me
>that something in the curricula in those states is teaching this particular
>subject more effectively than the other parts of the country.
>
>There are 350+ questions, and, like I say, there are lots of missing values.
>There is no single question that each student took.
>
>So my question is, how do I determine which questions are good at this
>discrimination? I've been trying to cast it as a regression problem, but I
>don't think that's it. Is this a case for something like Fisher's
>Discrimination analysis? I've only got passing familiarity with the
>technique.
>
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_________________________________________________________
dennis roberts, educational psychology, penn state university
208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED]
http://roberts.ed.psu.edu/users/droberts/drober~1.htm
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