Issues raised in the studies:
- it is difficult and time-consuming to codify and quantify comments from discussion boards.
- differences between instructor experience, training, and teaching approaches (e.g., "craft-oriented practices" (Saba, 2001)
- variations among student achievement and characteristics
- normal "ebb and flow" class variations
- "Courses are participatory experiences shaped by the learners themselves, making each individual offering a unique entity" (Sener - pg 1). Examples include media attribute theory, social presence theory, content analysis, systems dynamics and discourse analysis
- studies include different subjects
- varying student demographic data and prior knowledge
- varying student technical skills
- difficult and impractical to assign learners randomly to classes for studies (Sener - pg 1)
- varying student and teacher knowledge of collaboration techniques
- varying teacher knowledge of online moderation techniques
- varying perceptions about online and f2f learning
- varying assessments. The Rice report (pg 432) cites Bernard et al. (2004) who found that studies that involved researcher-made tests favored distance learning over face-to-face, while studies using teacher-made tests favored face-to-face classrooms over distance learning.
- "various alternative approaches to evaluating online learning within its own frame of reference" (Sener - pg 3)
- studies use different technology tools and online pedagogies
- the technology tools and pedagogy may shift over time and between studies
- varying degrees of learner support
- what was the social environment like for students (this may not be visible by the teacher)
- varying degrees of course material quality