Dear all =20 I have a question about combining data on species attributes when the attri= butes are measured on an ordinal scale (i.e. less than or more than, 1 < 2 = < 3 <4 but the intervals between the scores or ratings are not equal). Norm= al mathematical operations (+ - x) generally are not permitted. What I woul= d like to do though is use those ordinal values when combining them so that= a species with attribute a=3D1, b=3D1, c=3D1 is different from a=3D1, b=3D= 1, c=3D2. I can do that it seems by working out all the combinations and th= en ranking those. The issue then bcomes the order in which I sort the attri= butes to find the combinations. For example what are the relative rankings = of a=3D1, b=3D1, c=3D1 and a=3D1, b=3D1, c=3D2 and a=3D1, b=3D2, c=3D1. I c= an do that but it becomes very laborious with a large data set (90+ species= ). Would it be legitimate to use mathematical operations on the ordinal dat= a just to get the relative ordering right for the final ranking, and not fo= r any statistical tests? =20 Ordinal data often are used in questionnaires but the data are analysed dif= ferently, for example using clustering and constructing tree diagrammes. Al= l I want is a logical and recognised method for combining attrubutes rated = on an ordinal scale. =20 Or has anyone got any other suggestions?=20 =20 Thanks =20 David =20 David C Le Maitre Conservation Biologist - Hydrologist Natural Resources and Environment CSIR P.O. Box 320 Stellenbosch 7599 South Africa e-mail: [EMAIL PROTECTED] Tel: +27 21 888 2407/2460 Fax: +27 21 888 2684 Cell: +27 72 337 0657=20 =20 =20
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