----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, May 22, 2000 1:15 AM
Subject: Cumulative Frequency Polygons a right way?
>
>
> Hi all,
>
> First up, the purpose I have at hand is to make interpolations for
> percentages of students who have achieved above a certain score on a
> test (where this score may lie between two discrete score points on the
> scale)
_____
ETC (see his original)
I have always assumed that the Kaplan-Meier estimator is the accepted
plotting method. You will find this in one of your stat books or in some
text on failure-time analysis.
For large bin sets there is very little difference between the three
positions you give.
DAHeiser
> It seems to me cumulative frequencies should be plotted at the exact
> upper limit of each interval. This is the only simple method that
> makes sense to me.
>
> However, it has been suggested by others in the context I'm dealing
> with that frequencies/percentages can alternatively be plotted at the
> mid-point of each interval, or even at the lower limit! Although I can
> understand plotting graphs at the mid-point for ease of representation,
> this hardly seems suited to making interpolations. This is because
> when you read off the graph at the upper limit of a given interval, you
> will (probably) have more cases than fell up to and including the
> interval itself. This is surely absurd, yet people seem to seriously
> believe it is a viable alternative.
>
> I'm really hoping for a good reference on this (preferably by a highly
> regarded author to make the case stronger :). Any comments? Any nice
> references?
>
> Thanks!
>
> Steve.
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>
>
>
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This list is open to everyone. Occasionally, less thoughtful
people send inappropriate messages. Please DO NOT COMPLAIN TO
THE POSTMASTER about these messages because the postmaster has no
way of controlling them, and excessive complaints will result in
termination of the list.
For information about this list, including information about the
problem of inappropriate messages and information about how to
unsubscribe, please see the web page at
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