The internal consistency, scalability, and criterion validity of the GFI subscale Health Problems is less strong (Cronbach's α = .57, Hs = .35, r = −.48).
The subscales Daily Activities and Psychosocial Functioning showed good internal consistency, scalability, and criterion validity (Daily Activities: Cronbach's α = 0.81, Hs = .84, r = −.62; Psychosocial Functioning: Cronbach's α = 0.80, Hs = .35, r = −.48).
The internal consistency, scalability, and criterion validity of the GFI subscales Daily Activities (Cronbach's α = .81, Hs = .84, r = −.62) and Psychosocial Functioning (Cronbach's α = .80, Hs = .54, r = .67) are good.
Scalability, internal consistency and distribution scores were calculated for each predefined subscale using the Mokken scale analysis.
The aim of this study is to evaluate the scalability and internal consistency of the German version of the QUALIDEM.
The subscale Health Problems showed less strong internal consistency but acceptable scalability and criterion validity (Cronbach's α = .57, Hs = .35, r = −.48).
The large correlation with previous findings with respect to the scalability and internal consistency of the adopted subscales supports the validity of the study results [ 12, 26].
The results show an acceptable scalability and internal consistency for seven QUALIDEM subscales for people with mild to severe dementia and three subscales for people with very severe dementia.
Concerning the subscales having something to do (mild to severe dementia), negative affect and social relations (both very severe dementia), the extent to which rewording of the items produces better scalability and internal consistency should be explored.
This difference should have no effect on the results of the scalability and internal consistency because the 18 items for very severe dementia were also assessable for this group.
