>Hi
>
>On Tue, 9 Oct 2001, Payam Heidary wrote:
>> This week I lectured on various levels of measurement
>> i.e., ordinal, nominal, interval, ratio, etc. in
>> research and I found that some students have a hard
>> time understanding these concepts. DO anyone of you
>> have a good strategy or method for clearly explaining
>> these concepts or any good handouts you can share with
>> me. Would appreciate your input on this matter. Thanks
>
>One perhaps unacceptable possibility is to skip it, and just
>discuss the distinction between categorical (i.e., nominal) and
>numerical (i.e., the rest). The differences among ordinal,
>interval, and ratio do not matter for the statistics, and, I
>suspect, will generally never be used again by undergraduates.
>
>Best wishes
>Jim
That's not quite true. You shouldn't use a t test for ordinal data. I generally
distinguish between nominal ("categorical"), ordinal ("ranked") and interval/ratio
("continuous") data. The interval/ratio distinction is not important for selecting a
statistical test; however, you shouldn't compute a percent change on interval data
(e.g. 20% reduction in RT is okay, but 10% improvement in SAT scores doesn't make
sense since there is no true zero). However, I am teaching at the graduate level.
Charlotte
--
======================================================
Charlotte F. Manly, Ph.D. | Psychological & Brain Sciences
Assistant Professor | 317 Life Sciences Bldg
ph: (502) 852-8162 | University of Louisville
fax: (502) 852-8904 | Louisville, KY 40292
[EMAIL PROTECTED]
http://www.louisville.edu/a-s/psychology/
http://www.louisville.edu/~cfmanl01
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