Emil O W Kirkegaard

single self reported items have substantial measurement error.

huh. Like comparing yourself to your friends and thus adding bias? Other measures give smaller or bigger gaps?

This question makes little sense tome. Look into self vs. other ratings. http://www.ncbi.nlm.nih.gov/pubmed/21038940 

It's a no-brainer that single items are not so reliable, i.e. random measurement error. https://en.wikipedia.org/wiki/Spearman%E2%80%93Brown_prediction_formula …

yes, I just meant as in, supposing a bigger sex dif than that and most people having mostly same-sex friendships…

maybe a very emotional male rates himself very high compared with his male friends, while having something...

not unusual in females. that being said thanks for the answer and links.

You are talking about the problem with these implicit comparison group, questions. I agree. Prefer ratio scale.