Keep it civil, please.
Quote:
Originally Posted by tompe
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There's a big difference (more than an order of magnitude) between 24 and 350. And I prefer the 5% error margin, so one would need at least 500 participants to design a study, even using these guidelines.
The other problem with these guidelines is that they don't take the complexity of the sample into account. If you need to control for several variables, your sample size needs to be higher to be sure you've adequately represented everyone. In this case, we should be looking at the type of material being read, the reading ability of the participants, vision issues, language of the materials and primary language of the reader, level of comfort with technology of the reader, reading conditions (e.g. outdoors in daylight vs. in a well-lit room vs. in a dimly-lit room), etc. Essentially, any circumstances you want to be able to generalize across need to be taken into account in your sample selection. (If you only want to be able to generalize to American full-time college students at four-year public institutions, your sample probably wouldn't need to be as large.)
In this case, the results of the comparison were not found to be significant. That's partly
because of the small sample size. A study of this size doesn't have sufficient power to detect a significant difference, even if there is one. The qualitative data collected (the participants enjoyed the experience of using an ebook reader) is fine, though not generalizable. A study of this type can be useful to generate hypotheses which could be tested in a larger, more quantitatively rigorous study. But no conclusions can be drawn from the study as presented.
(And for those who wonder about my qualifications, I'm working on a dissertation involving quantitative research in the use of technology in the learning process-- not that far from the stated goals of this study.)