lecture 10 from a college level research methods in psychology course taught in the spring 2012 semester by Brian J. Piper, Ph.D. (psy391@gmail.com) at Linfield College
3. Terminology
• ceiling effects:
• floor effects:
• factorial design: more than 1 independent variable
–2x3
–3x4
– 2 x 5 mixed (2 between group, 5 within groups)
• factorial matrix (2 x 2) with 4 cells (conditions)
Males Females
Drug 1st 2nd
Placebo 4th 3rd
• main effect: overall effect of an IV (sex or drug)
4. Terminology
• Ceiling effects: mean score near maximum
• Floor effects: mean score near minimum
• factorial design: more than 1 independent variable
–2x3
–3x4
– 2 x 5 mixed (2 between group, 5 within groups)
• factorial matrix (2 x 2) with 4 cells (conditions)
Males (A1) Females (A2)
Drug (B1) 1st 2nd
Placebo (B2) 4th 3rd
• main effect: overall effect of an IV (sex or drug)
6. Examining Main Effects
• Main Effects (continued)
– Calculations row and column means
– For hypothetical data:
• Row mean #1 mean of 17 and 23 (= 20)
• Row mean #2 mean of 12 and 18 (= 15)
• Column mean #1 mean of 17 and 12 (= 14.5)
• Column mean #2 mean of 23 and 18 (= 20.5)
7. Main Effects
• Male and Female college students (N=89)
were assigned to different encoding intervals
(3, 6, 9, 12, or 15) with the Novel Faces and
Places (NFAP) test.
• This design is _____ x _____
11. More Main Effects
• Attractiveness rating at different times among
bar patrons
Mickey Gilley (1 min): http://www.youtube.com/watch?v=2e2qsnHVAo4&feature=fvst
12. More Main Effects
• Attractiveness rating at different times among
bar patrons
Mickey Gilley (1 min): http://www.youtube.com/watch?v=2e2qsnHVAo4&feature=fvst
13. Interaction
• The effect of one IV (A) depends on the level
of another IV (B)
• Possibilities:
A B AxB
- - -
- - +
+ - -
+ - +
+ + -
- + -
- + +
+ + +
14. Interaction (but no main effect)
Example #1
• Interactions
– IVs course emphasis and student major
– No main effects (row and column means all equal 75)
16. Self-Test
• Rats were exposed to MDMA or Saline during
adolescence (age 35 to 60) and locomotor
activity tested at age 65
• Time Main Effect: ?
• Drug Main Effect: ?
• Interaction: ?
Piper et al. (2007) Developmental Psychobiology, 47, 145-157.
17. Example
• Rats were exposed to MDMA or Saline during
adolescence (age 35 to 60) and locomotor
activity tested at age 65
• Time Main Effect: Yes
• Drug Main Effect: No
• Interaction: Yes
Piper et al. (2007) Developmental Psychobiology, 47, 145-157.
18. Emotional Labeling
• Participants (N=32) are asked to label
emotions of faces
Anger Fear
Direct
Averted
Adams & Kleck (2003) Psychological Science, 14, 644-647.
19. Emotional Labeling
• Participants (N=32) are asked to label
emotions of faces
• Response time recorded (ms)
Anger Fear
Direct 862.3 (23.5) 944.5 (27.5)
Averted 914.1 (25.6) 891.2 (24.4)
Adams & Kleck (2003) Psychological Science, 14, 644-647.
20. Guess
• Main effect of direction: ?
• Main effect of expression: ?
• Interaction: ?
21. Guess
• Main effect of direction: No
• Main effect of expression: Yes
• Interaction: ?
Adams & Kleck (2003) Psychological Science, 14, 644-647.
22. Guess
• Main effect of direction: No
• Main effect of expression: Yes
• Interaction: Yes
Adams & Kleck (2003) Psychological Science, 14, 644-647.