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I have requested 30 participants to answer the same question about 100 images: "How easy is it for you to recognize this image?" on a scale from 0 to 100, where 0 is easy and 100 is difficult.

I want to 1) eliminate extreme scores, so the closer they are to 100, the more unfavourable these images will be to me. 2) I would like to identify participants with extreme scores, so for instance if they were bored and they have different scores than the rest I would like to identify these.

Would I do a simple descriptive analysis to see whether some participants have higher means than the rest (or look at standard deviations)? Also, how can I compare the scores on the images, would a graph with frequencies do the trick?

Thanks for your time!

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  • $\begingroup$ It's not just about standard deviation for each question, but I would need to find a test to see if there are statistically significant differences between questions. Of course I would like to rule out outliers (which I can deal with), but I need to compare the results for each question. $\endgroup$ – Roxy Mar 23 '16 at 22:37
  • $\begingroup$ Questions solely about how software works are off-topic here, but you may have a real statistical question buried here. You may want to edit your question to clarify the underlying statistical issue. You may find that when you understand the statistical concepts involved, the software-specific elements are self-evident or at least easy to get from the documentation. $\endgroup$ – gung Mar 23 '16 at 23:27
  • $\begingroup$ Thanks for your message. It is related to stats, I'm not worried about the software, but more so about the theoretical approach to solving the statistical question. $\endgroup$ – Roxy Mar 24 '16 at 19:18
  • $\begingroup$ Then you may want to edit your Q to emphasize the statistical issues that you need clarified & deemphasizing the software-specific aspects. $\endgroup$ – gung Mar 24 '16 at 19:25
  • $\begingroup$ What is the ultimate goal of doing this? Why do you want to identify images of middling difficulty & participants of middling ability? $\endgroup$ – gung Mar 24 '16 at 19:30

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