In article <[EMAIL PROTECTED]>,
Rich Ulrich <[EMAIL PROTECTED]> wrote:
>On 2 Jul 2002 07:46:20 -0700, [EMAIL PROTECTED] (nothanks) wrote:
>> Hello all,
>> I have a client who wants to compare the relationship/association
>> of two variables (Y1 and Y2) between 2 groups (say Gender).
>> They (statistically challenged) have left it to me to decide
>> on method (and how to measure association).
>> Y1 and Y2 are ordinal, but are actually continuous variables
>> binned into 0, .5, 1, 2 and 3. So, I'm o.k. with treating them
>> as continuous.
>Well, do look at the crosstabulation, if not at the plot of
>raw numbers. Is the association linear?
>Does the differential spacing (half-point
>and one-point) suggest that you ought to rescale each
>interval to 1.0 ?
I suggest that you point out what your client needs to state
for you to be able to help rationally. Here are my five
commandments for clients and consultants; you can decide
on the statistical method, but not how to measure association.
I am often requested to repost my five commandments. These are
posted here without exegesis.
For the client:
1. Thou shalt know that thou must make assumptions.
2. Thou shalt not believe thy assumptions.
For the consultant:
3. Thou shalt not make thy client's assumptions for him.
4. Thou shalt inform thy client of the consequences
of his assumptions.
For the person who is both (e. g., a biostatistician or psychometrician):
5. Thou shalt keep thy roles distinct, lest thou violate
some of the other commandments.
The consultant is obligated to point out how their assumptions affect
their views of their domain; this is in the 4-th commandment. But the
consultant should be very careful in the assumption-making process not
to intrude beyond possibly pointing out that certain assumptions make
large differences, while others do not. A good example here is regression
analysis, where often normality has little effect, but the linearity of
the model is of great importance. Thus, it is very important for the
client to have to justify transformations.
There are, unfortunately, many fields in which much of the activity
consists of using statistical procedures without regard for any assumptions.
--
This address is for information only. I do not claim that these views
are those of the Statistics Department or of Purdue University.
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
[EMAIL PROTECTED] Phone: (765)494-6054 FAX: (765)494-0558
.
.
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