However, if the number of items is inferior to 5, it is possible to obtain a low alpha coefficient (around 0.65) whereas if the number of items is superior to 10, the value of the alpha is higher (around 0.90).
The very low alpha coefficient for the Self Directed Aggression scale was expected because it only consists of two items, and the alpha statistic is to some extend a function of the number of items in a scale.
The low to modest alpha coefficient of the SDQ subscales in the present study, including the primary outcome indicator (SDQ-ES), is something of a concern.
Our findings of low alpha coefficients in the BS and TS domains of the EORTC QLQ-PR25 are similar to those have been previously reported.
However, five results, in Q36 and Q42, reflected low alpha coefficients (<.60): "gross motor" (Q36 and Q42), "problem solving" (Q36), and "personal-social" (Q36 and Q42).
The lowest Cronbach alpha coefficients in those studies were found in Japan and seemed to be connected to that particular cultural background [ 10].
Although these reliability coefficients were somewhat low, it is not uncommon to have low Cronbach's alpha coefficient value for scales including less than ten items (Pallant 2007).
The reliability coefficients for "perceptions of the factors that impede addressing evolution in their classrooms" and "personal science teaching efficacy beliefs regarding evolution" were somewhat low; however, it is not uncommon to have low Cronbach's alpha coefficient value for scales including less than ten items (Pallant 2007).
Lastly, the low Cronbach's alpha coefficient of the social domain of the WHOQOL-Bref limits the reliability of the findings for this domain.
It has been suggested that scales with smaller number of items could have low Cronbach's alpha coefficient values [ 14] as recorded in the parents' participation in school scale.
