Posted by
student09 on
Mar 18, 2011; 9:32am
URL: http://spssx-discussion.165.s1.nabble.com/Cell-sizes-Orthoplan-tp3964555.html
Dear All,
I would be very glad if somebody might help me with the following question -
I need to conduct a factorial survey (a.k.a vignette study).
- There are 2 factors A and B.
- Factor A has 4 conditions, B has 5 conditions.
- It is a between-subjects ANOVA design.
I now want to gauge the minimum number of person needed for this study.
This is of course a question of test power, but my problem relates to a
rather specific aspect, namely:
The total number of cells would be 4*5=20.
However, should I consider the number of people per condition within each
factor (that would be 4 respectively 5)OR the number of people across all
possible combinations (the 4*5 = 20 cells) to gauge the sample size needed?
Obviously, even if one follows the rule of thumb of "use 25 obersvations
per cell", the conclusions would be quite different, because then I would
either had to use 4*25 = 100 respectivley 5*25 =125 people, or 20*25= 500
people
What would be the appropriate view here?
Many thanks for your ideas!!!!
Lea
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