Context: In my real experiment I am planning to include a questionnaire. I aim to measure 4 different constructs with multiple questions per construct. The questionnaire now consists of 24 items. I created more questions than I need with the idea of doing a pre-test and then reducing the number of questions to 12 based on the results of factor analysis.
I was thinking of having a sample size of 30 people to participate in my pre-test, but is just what I came up with.
Question: What is the minimum sample size required for exploratory factor analysis in order to reliably refine a multi-factor questionnaire?