How to Find Twins within a Dataset (Cases with Same School, Teacher and Birthdate)?

[Justin Meyer-3]

Hello SPSSlisters,

 

I would like to find all the cases of twins within a dataset of
thousands of students. This means I need to find all the cases where the
School, Teacher, and Birthdate are the same. Why? Because I am matching
up student pre and post test scores on these variables (when student
number is not available) and I need to know the cases where these
variables won't be able to distinguish between two students. I have
considered using gender to further distinguish, but this may only work
in some cases.

 

I am a beginning syntax user and I have no knowledge of more advanced
techniques at this time, although I am willing to try. I have not yet
tried to write any syntax for this because I don't really even know
where to start.

 

Thanks for any help you can provide.

 

____________________________________

Justin Meyer

Researcher

Rowland Reading Foundation

1 South Pinckney Street, Suite 324

Madison, WI  53703

phone: [phone]  fax: [phone]

www.rowlandreading.org <http://www.rowlandreading.org/>

____________________________________

 

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[Maguin, Eugene]

Justin,

>>I would like to find all the cases of twins within a dataset of
thousands of students. This means I need to find all the cases where the
School, Teacher, and Birthdate are the same. Why? Because I am matching
up student pre and post test scores on these variables (when student
number is not available) and I need to know the cases where these
variables won't be able to distinguish between two students. I have
considered using gender to further distinguish, but this may only work
in some cases.

There are at least two ways to do this and this is one way.

Aggregate outfile=* mode=addvariables/break=school teacher
birthdate/twin=nu.

What you will get is your original datafile with a new variable, twin,
added. Twin will have values of 2 for cases where two records have the same
values for school, teacher, and birthdate, 3 for record triplets, etc or 1
for singletons.

Gene Maguin

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