How many variables should I use for clustering a huge dataset?
<p>I've conducted a series of long-term surveys with a same group of 44 respondents (not that many, but I could not do better).</p>
<p>I need to cluster the sample in SPSS using two-step analysis, however there are really a lot of variables. As 6 different survey questionnaires were conducted, there are about 200 quantitative questions (variables), let alone the qualitative ones.</p>
<p>My first question is: should I use all the quantitative variables to perform the cluster analysis? All manuals I read choose some selected variables for the clustering solution, instead of all of them.</p>
<p>The second problem is that I attempted to use hierarchical clustering with all the quantitative data, but SPSS notified that:</p>
<blockquote>
<p>Warnings</p>
<p>Not enough valid cases to perform the cluster analysis.</p>
</blockquote>
<p>...which means the data set I have cannot be used to perform cluster analysis... In this case what should I do to perform the cluster analysis?</p>