Awfully, the standard deviations of almost every item in their validation study [1, Table 1] is greater than the means --in some cases even twice as big--, which themselves are very low (the majority are below 2, and several are below 1). This is, at a minimum, strongly indicative of bimodality --which would make sense since, among other things, participants were drawn mostly from Bonn University's lucid dreaming student club [p.11]. As a matter of fact, they report they threw away two data sets (!) precisely because of "extreme answering style (all items were scored as 0 or 5)" [ibid].
Why they didn't heed these warning signs (and at the very least use medians instead of means from then on) is beyond me.
Awfully, the standard deviations of almost every item in their validation study [1, Table 1] is greater than the means --in some cases even twice as big--, which themselves are very low (the majority are below 2, and several are below 1). This is, at a minimum, strongly indicative of bimodality --which would make sense since, among other things, participants were drawn mostly from Bonn University's lucid dreaming student club [p.11]. As a matter of fact, they report they threw away two data sets (!) precisely because of "extreme answering style (all items were scored as 0 or 5)" [ibid].
Why they didn't heed these warning signs (and at the very least use medians instead of means from then on) is beyond me.
[1] http://www.blogs.uni-mainz.de/fb05philosophie/files/2013/04/...