complex research designs Flashcards
(11 cards)
Complex Designs
two or more IVs are
manipulated simultaneously in a single experiment
complex designs =
factorial designs
involve factorial combination of the IVs
All levels of one IV paired with all levels of the other
Interaction:
- When the effects of one variable depend on the level
of another variable - When the effects of one variable are different for
different levels of another variable - You can’t discuss the effect of one IV without
considering the level of the other IV
Ex: “Drug interaction precaution” on medicine – Drug A and Drug B alone may be helpful, but Drugs A and B
together may be harmful
Describing factorial designs
2 x 3
- NUMBER of numbers = NUMBER of IVs (in this case, two IVs)
- VALUE of numbers = levels of each IV (in this case, one IV has
2 levels, the other has 3) - product of numbers indicates total number of conditions (in this case, 2 x 3 = 6
We can evaluate a main effect for each independent variable
(e.g., if there are two IVs, there can be 0, 1, or 2 significant
main effects)
We can evaluate the interaction between the two IVs (the
interaction may or may not be significant)
The simplest factorial design is a…
2x2 design (two IVs, with
two levels for each IV)
- something with less than two levels is not a variable
Identifying main effects and interactions from graphs
- Lines that are parallel indicate no interaction
- Lines that are not parallel indicate that an
interaction may exist
what test should you use to determine if the main effects and interaction
are truly statistically significant?
ANOVA (one-way, tow-way, etc.)
“There is a main effect of variable A.” =
“The main effect of variable A is significant.”
“There is no main effect of variable A.” =
“The main effect of variable A is not significant.”
Computing an ANOVA allows us to…
evaluate the
significance of main effects and interactions
Mixed factorial design:
One IV is independent groups,
the other is repeated measures
