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Date:         Mon, 14 Feb 2005 12:05:17 +1030
Reply-To:     "Barnett, Adrian (HEALTH)" <adrian.barnett@HEALTH.SA.GOV.AU>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         "Barnett, Adrian (HEALTH)" <adrian.barnett@HEALTH.SA.GOV.AU>
Subject:      Re: Comments on SPSS documentation
Comments: To: Dale Glaser <glaserconsult@sbcglobal.net>
Content-Type: text/plain

Hi Dale (again) I accidentally posted this to Dale alone, and am sending to the whole list this time (sorry Dale! - thanks for your reply) as I'd like it to get a bit more coverage - especially with people from SPSS.

Hi I'd have to agree with you there. To some extent they have gone backward. The older manuals were very enlightening on the statistical procedures used. They were not a substitute for a text on the topic, but, given the wide divergence in notation used by different texts, it was especially useful to see how the procedure had actually been implemented. Picking up several texts on a subject will not often enlighten you on where an how a particular thing is in the output. Marija Norusis' manuals were excellent for this. Even the old magenta-coloured manual from the 1970s was a pretty good intro to a whole range of procedures.

Whilst I can see that it's not possible for SPSS to essentially write stats texts they cannot just give a syntax for a procedure and leave you to work out for yourself how it relates to what the textbooks cover.

In one area of syntax explanation they've gone backwards too. I've always been baffled by the explanation of the third parameter on the INDEX command, and consequently just ignored whatever it was trying to say. I puled out the 1983 edition of the SPSS-X User Guide and was amazed to find that there had been a separate section which explained this and which has since been removed form the manual. For the benefit of the list, I will reproduce it below.

"7.18 The third argument of INDEX.

The third argument of INDEX is helpful when you need to look for more than one character or set of characters in a string. For example, the expression (INDEX,'MISSISSIPPI','LLSS',2) looks for either LL or SS. If the number of characters in the second string is not evenly divisible by the third argument, it is an error. If INDEX finds more than one string, it returns the smallest index value. For example, the function (INDEX,'MISSISSIPPI','PPSS',2) returns 3, not 9.

The most useful application of the third argument of INDEX is looking for one among several special characters. For example, if two variables have been recorded in two columns separated by either a blank, a comma, or a semicolon, you could separate the variables by reading the data as a string and separating it into numeric variables, as in:

DATA LIST NOTABLE /#VAR (A5)

COMPUTE #DELIM = INDEX(#VAR,' ,;',1) COMPUTE VAR1 = NUMBER(SUBSTR(#VAR,1,#DELIM - 1),F2) COMPUTE VAR2 = NUMBER(SUBSTR(#VAR,#DELIM + 1),F2)

PRINT /VAR1 VAR2 (F2,1X,F2) BEGIN DATA 1 2 1,4 3,4 4,3 6;3 10 2 11;4 4 10 END DATA

#VAR is a scratch variable (Chapter6) used to read the first five columns of data as a single alphanumeric variable, and #DELIM is a scratch variable that stores the position of the delimiter character. In the COMPUTE command for variable VAR1, SUBSTR(VAR,1,#DELIM - 1) says "Return the substring of #VAR starting in the first position and ending one position before a blank, comma or semicolon." Then SUBSTR(#VAR,#DELIM + 1) returns the substring starting one position after any of these characters to the end of the string. The two substrings are converted to numbers using the NUMBER function (see Section 7.17). The PRINT display output is shown in Figure 7.18."

I think that without this bit, the explanation in the INDEX function of the 3rd parameter is entirely opaque. What a shame someone decided that 7.18 was worth removing!!

The manual then goes on to explain that you can nest functions, a handy technique that is no longer explained in the current manuals and which many users would probably never work out for themselves. The explanation in the section also provided valuable insights into how the different nested functions worked, even in isolation. Another valuable piece of information now lost.

I appreciate that the SPSS package is now much bigger than it was back then, and requires much more stuff explained. However there is no longer an argument based on problems of distributing many bound manuals, since this is not done unless you buy them.

I think it is a pity that things which were once there, and were very useful - and even indispensable, as in the above example - were discarded.

Regards

Adrian

-- Adrian Barnett Research & Information Officer Ph: +61 8 82266615 Research, Analysis and Evaluation Fax: +61 8 82267088 Strategic Planning and Research Branch Strategic Planning and Population Health Division Department of Health email: Barnett.Adrian@saugov.sa.gov.au

God is good but don't dance in a currach. - Irish proverb

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-----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of Dale Glaser Sent: Sunday, 13 February 2005 5:49 To: SPSSX-L@LISTSERV.UGA.EDU Subject: Comments on SPSS documentation

In the years of using SPSS since mainframe days, and the few years I have been on this listserv, I have never used this as a forum for gripes, but I'd like to register a minor one and see if I'm in the minority!! This past week I had the opportunity to use PLUM for proportional odds modeling (AKA: ordinal regression). When I accessed the manuals to aid in interpretation of the Threshold and Location parameters, they are woefully amiss in shedding any insight. Though I had a suspicion that the Threshold parameters are calculated similarly to how the same parameters are calculated via PRELIS for deriving the polychoric correlation matrix, I wanted unequivocal confirmation of such, which the manuals do not do (though I can always access the statistical algorithms if need be). That being said, doesn't it seem in the "good old days" the SPSS manuals actually were fairly illuminating in the mathematical/statistical details in the output? I actually found them, alongside other texts, to be very educational. Nowadays, the manuals are just on the CD and even then , they are nothing more than details on point-and-click. Reading Long's "Regression Models for Categorical and Limited Dependent Variables" last night made very clear the interpretation for both the proportional odds model and multinomial logistic model, but it would be nice to have that level of information in the SPSS manuals.

Just a comment/frustration that I wonder if other SPSS users also have........thank you...Dale

Glaser Consulting Dale Glaser, Ph.D. Consultant/Lecturer (SDSU/USD/AIU) 4003 Goldfinch St, Suite G San Diego, CA 92103 phone: 619-220-0602 fax: 619-220-0412 email: glaserconsult@sbcglobal.net website: www.glaserconsult.com


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