```Date: Thu, 4 Oct 2007 13:20:12 -0300 Reply-To: Hector Maletta Sender: "SPSSX(r) Discussion" From: Hector Maletta Subject: Re: calculating an index Comments: To: Dirk Sebastian Friedrich In-Reply-To: Content-Type: text/plain; charset="us-ascii" Dirk, I do not really see your difficulty. If you simply want to add the score over the five questions, each with a 7-point scale ranging from 7 to 1 in a reverse scale (7 is low and 1 is high), your index might be the sum or the average of the five questions, period. Examples: COMPUTE INDEX=SUM(QUESTION1,QUESTION2,QUESTION3,QUESTION4,QUESTION5). COMPUTE INDEX=MEAN(QUESTION1,QUESTION2,QUESTION3,QUESTION4,QUESTION5). I'd recommend the MEAN function, just in case somebody omitted responding some of the five questions. Also, you may specify (as an argument to the MEAN function) the minimum number of non-missing questions required to compute the mean, writing for instance MEAN.3 if you require at least three valid responses for the index to be computed validly. Now, this kind of index is a very simple one, giving the same weight to each of the five questions. You might use a more sophisticated approach such as CATPCA (with input variables defined as ordinal) which is included in the SPSS CATEGORIES module, to generate a principal component analysis for categorical variables, and using the score of the main component as an index. Note that the simple index with COMPUTE assumes that the scores in the questions are interval scales, which may not be right. Assuming they are interval scales you may also apply classical factor analysis with the FACTOR command. These commands, CATPCA or FACTOR, give each of the five questions a different weight, and take their inter-correlation into account. Hector -----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of Dirk Sebastian Friedrich Sent: 04 October 2007 12:11 To: SPSSX-L@LISTSERV.UGA.EDU Subject: calculating an index Dear members, I've got a general problem concerning the structure of SPSS . What I want to do is calculating an index about the benefit of a product group. I've got 5 questions each asking for the benefit of a different product and 7 answer options per question (1=high benefit to 7=low benefit). What I need to do now, is adding up all answers per answer option of the 5 products, for being able to calculate the mean (=my benefit-index of all the products). That's exactly the step where I am failing. (For the "usual" SPSS-way the column for calculating would be 5 times long as before.) I want to be able to research other answers of a survey against the background of the index. Is there anyone who knows what I can do for calculating the index in SPSS and still being able to conduct further analysis against the background of the index. Thanks in advance! Dirk ```

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