Hello. I'm hoping some of you might be able to help me with the following
statistical problem. I have a sample of about 2500 subjects, each of which
has been grouped into 1 of a possible 70 categories (based on their behavior
and other criteria). Out of that data, I've created a table listing those
categories in descending order according to the frequency with which each
occurred in the sample. For example:
1) category 6 17%
2) category 35 13%
3) category 65 7%
4) category 2 3%
.
70) category 40 0.1%
-------------------------
total 100%
I was interested in how the frequency table would change with increasing
sample size, so I took 500 of my subjects and created a frequency table for
them, then took another 500 and added it to the previous sample and
recreated the table, and so on until all subjects had been added to the
pile. As you might expect, the table tended to stabilize as sample size
increased. The problem is, it's important to my project to ensure the
accuracy of the ordering within the table for the top fifth of the
categories-in other words, I need to be reasonably certain (p = .01?) that
the top, say, 15 categories in my table actually are the 15 most common
categories occurring within the population, and also (less importantly) that
their relative frequencies correspond to the ranking indicated by the table.
Is such a determination possible? Or, looking at the question another way,
is it possible to determine the optimal sample size for achieving a stable
frequency table? And if so, can you point me in the right direction?
Thanks very much for any help,
Mike
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