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  1. purifyz

    Which type of time series to use?

    Hey, I have a data set which includes weekly/monthly sales and questions about customer satisfaction. I have already done EFA/CFA based on these satisfaction questions (turns out it's just one satisfaction factor) I would like to regress sales on satisfaction, but I think I should include a...
  2. purifyz

    convenience sampling and p-values

    Dear all, I am in the middle of my research. I gathered data (via convenience sampling). I intend to run PCA/EFA and then use dimensions in logistic regression model. Since my sample is nonprobabilistic I can not formulate any inferences about population. My question is - what do I do with...
  3. purifyz

    covariance matrix vs correlation matrix

    Dear all, I am now studying PCA/FA and stumbled upon following problem: if variables are measured on different scales it's reasonably obvious that we should use correlation matrix. But, when one should use covariance matrix if variables have the same scale? Jolliffe wrote that there might be...