Fig. 1From: Structural validity of the Boston Carpal Tunnel Questionnaire and its short version, the 6-Item CTS symptoms scale: a Rasch analysis one year after surgeryDifferential item functioning by gender for item 6 (“How often did the following symptoms in your hand wake you up at night? - numbness or tingling”) of the CTS-6. Note in figure: ‘Some person location values … decrease minimum location’ and ‘Person location’Back to article page