Interactions

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Interactions

• PSYC 3070

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Interactions

• Researchers who employ factorial designs (more
  than one IV) often are interested in the
  interactive effects of the IVs on the DV
• An interaction is said to exist when the
  influence of one IV on the DV is significantly
  determined by the level of another IV

3
Interactions

• The interaction concept is one of the most easily
  misunderstood
• Most people confuse additive effects with
  interactive effects
• An additive effect means that more than one IV
  has an influence on the DV
• There is more to an interaction than this

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Interactions

• Lets say you are looking at the effects of speed
  and agility on the performance of basketball
  players.
• Players are divided into high and low groups
  on both IVs and rated on a 1-5 scale for overall
  performance

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Is this an interaction?
No interaction, just two main effects
6
Is this an interaction?
No interaction, just two main effects
7
Is this an interaction?
YES agility only matters if you are fast
8
Is this an interaction?
YES Agility matters more if you are fast
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Interactions

• Research example from the Smith Woody (2000)
  article in Teaching of Psychology

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Multimedia Teaching

• A frequent suggestion is that modern students are
  more visually oriented learners
• This suggestion is difficult to test
• However, it is reasonable to assume that
  differences exist in the extent to which students
  are visually oriented

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Multimedia Teaching

• To the extent that a visual learning style makes
  one more receptive to the multimedia approach, we
  should observe an interaction between learning
  style and instructional approach
• Those with the greatest degree of visual
  orientation should be the primary beneficiaries
  of multimedia teaching

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The Study

• Two sections of Introduction to Psychology were
  utilized
• One section received traditional, lecture based
  instruction
• The other section had the same notes, but saw
  them on Power Point along with graphics, and saw
  laserdisc clips and video clips

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The Study

• Students completed the Childers et al. (1987)
  visual processing index
• A median split divided the students into high and
  low visual orientation groups
• The dependent variables were the four exam scores
  and student ratings of instruction

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Results

• There was no overall difference in the exam
  performance of the two classes
• The multimedia class gave higher ratings of the
  instructor
• Performance was influenced by the interaction of
  time, class, and visual orientation

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Results

• The only significant difference on exam 1 was a
  main effect of class, F 9.30, p lt 05. The
  traditional class (M 69.3) outperformed the
  multimedia class (M 60.1)
• No differences emerged on exam 2

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Results Exam 3

• Is there an interaction?

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Results Exam 4

• Is there an interaction?

18
Interactions

• Often, the interaction is the effect that we are
  most interested inthe main effects are mundane
  or uninteresting
• And it pays to know how to spot them

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Job Satisfaction data (from Maier Brunstein,
2001) z-scores used to represent JS