Question bank size issue

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Allo V Psycho
Posts: 680
Joined: Sat Nov 16, 2019 8:18 am

Question bank size issue

Post by Allo V Psycho » Tue Aug 29, 2023 5:15 pm

I've been asked by a organisation which runs national MCQ exams how many new items (questions) they need each year to maintain and perhaps extend their bank. I've suggested that the variables are:

N Total items in the bank
U Number of items used each year
P Proportion of items removed due to re-use (assuming an item can only be used so many times before it becomes known
R Number of items removed from the bank each year due to having become out of date
W Number of new items written each year
X Proportion of new items that can be used due to quality control issues
Y Year

Obviously, I'm thinking of an equation, and I have a pretty simple algebraic one which seems to work. But I've benefitted before from the collective wisdom here, so I thought I'd share the issue. Any great ideas?

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