Marc,
I just pulled my (old) copy of Gravetter & Wallnau off the shelf. They
define the range as the distance between the largest and smallest score in
the distribution. After thinking about this for a bit, it occurs to me that
using the real limits to calculate the range *may* be inappropriate because
what it really gives you is the *potential* range. If the highest score is a
5, it could potentially be 5.49, but it could also be 4.99. We don't know
for sure. In that case, calculating the range as Xlargest - X smallest (as
SPSS does according to their algorithm book) gives you a range on the actual
scores assigned rather than potential scores.
Thoughts worth everything you paid for 'em.
Regards,
Larry
************************************************************
Larry Z. Daily
Assistant Professor of Psychology
Department of Psychology
White Hall, Room 213
Shepherd College
Shepherdstown, West Virginia 25443
phone: (304) 876-5297
email: [EMAIL PROTECTED]
WWW: http://webpages.shepherd.edu/LDAILY/index.html
> -----Original Message-----
> From: G. Marc Turner [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, January 31, 2001 10:47 PM
> To: TIPS
> Subject: issue with stats course
>
>
> I need some advice on how to handle an issue in my stats course...
>
> I'm currently using the Essentials of Statistics (by Gravetter & Wallnau)
> as the textbook. In the chapter on variability, it uses the real
> limits for
> the calculation of the range, inter-quartile range, etc. This is actually
> how I learned to do the calculations by hand, and haven't really thought
> much about it until now.
>
> I'm also teaching the students how to use SPSS (v9) to get the same
> information after going over the hand-calculations. BUT, SPSS does not use
> the real limits when calculating the range, quartiles, etc. (For example,
> for one data set we get a range of 9 and an interquartile range of 1.89 by
> hand. SPSS calculates the range as 8 and the interquartile range as 2.)
>
> So, tomorrow afternoon when I go over this in class, and the students ask
> me to explain why the scores are different, what should the answer be? My
> immediate reaction is to say that we shouldn't trust the values of SPSS,
> and this points out why it is important to know how to do the calculations
> by hand. However, I'm not sure how far that will get me in convincing the
> students.
>
> Any suggestions are appreciated...
> - marc
> G. Marc Turner, MEd
> Lecturer & Head of Computer Operations
> Department of Psychology
> Southwest Texas State University
> San Marcos, TX 78666
> phone: (512)245-2526
> email: [EMAIL PROTECTED]
>
