I'm trying to see how level of scepticism impacts willingness to change diet. To measure sceptism I've used a 7 point likert scale. The study I'm basing my research on used a principal components analysis when analysing the Likert scale results to measure level of sceptism. I've got this far. But then the study uses a multinomial logistic regression to assess how skepticism effects willingness to change. Any idea on how to take the results of the PCA and put them into the MLA? (I'm using SPSS)
They obtain 5 explanatory variables. Then they apply PCA and get its first component score. Next, they run multinomial logit using that score as an explanatory variable, instead of the original 5 variables. PCA score is nothing more than a weighted average of the variables, except that the weights are chosen in a certain way.
I'm skeptical of this kind of studies. I bet you can get the same or similar result with a simple average of these 5 variables instead of PCA. In my opinion PCA is just a fancy method which doesn't add anything to this kind of data. It only makes it look more scientific.