Steve,
Your interpretation is right because the coordinates of the ogive (graph of
cumulative frequency/ relative cumulative frequency)) indicate " less than
the upper limit".
Jin
Jineshwar Singh, Coordinator, IDS
Interdisciplinary Department
George Brown College
St .James campus
[EMAIL PROTECTED]
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You cannot control how others act but you can
control how you react.
416 -415-2089
http://www.gbrownc.on.ca/~jsingh
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, May 22, 2000 2:08 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).
>
> 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, or refs?
>
> Thanks!
>
> Steve.
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>
>
>
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