One-Way Within-Groups ANOVA

19 Pages·2013·2.47 MB·English

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PSYC 381 – Statistics
Arlo Clark-Foos, Ph.D.
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• Pros of Between
• No order or
Between-Groups Design
carryover effects
• Pros of Within
• More costly
• Higgher variabilityy
between groups
than within
((ii.ee., iinnddiivviidduuaall ddiiffffeerreenncceess))
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Taste Tests
Odor Tests
What about
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Counterbalance!
• All participants experience all conditions/treatments/levels
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• Minimization of order effects by varying the order of presentation of
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group) to the next.
• An example of a counterbalanced within-subjects design with 3
conditions:
3 Conditions/Levels of IV
3! = 3 x 2 x 1 = 6 orders
What if your IV had more levels?
Example: IV = Year in School (4 levels)
4 x 3 x 2 x 1 = 24 orders!!
You need a Latin Square Design!
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A technique to control for order
effects without having all possible
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constructed to ensure that (1) each
condition appears at each ordinal
position and (2) each condition
precedes and follows each condition
one time.
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• New Terminology
• SS
Subjects
• df
Subjects
•• nn
• A few new formulas (along with the old ones)
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• Do you have a love of lagers?
• A journalist (Fallows, 1999) wanted to know if self-proclaimed
beer snobs would be able to distinguish between three
classes/qualties of beers. There are over 50+ styles of beer,
many of which are not available in lower quality versions so he
chose lagers because of their widespread availability. The
results below are their taste ratings for each beer.
• Cheap Beers
• e.g.,
• Mid-Range Beers
• e.g., Budweise
• High-End Beers
• e.g.,
One-Way Within Groups ANOVA:
Beer Taste Testing
• Six Steps to Hypothesis Testing…
1. Identify the populations,
1. People who drink cheap beer
2. Peopple who drink mid-rangge beer
3. People who drink high-range beer
• DDiissttrriibbuuttiioonn, FF ddiissttrriibbuuttiioonn ((>>22 ggrroouuppss))
• One-Way Within-Groups ANOVA
•• AAssssuummppttiioonnss
1. Participants not selected randomly, careful generalizing
2. Data do not appear skewed
33. HHomosceddasttiiciitty [[((llargestt variiance)) ≤≤ ((22 x smallllestt variiance))]]
4. Are there order effects? Not counterbalanced…
One-Way Within Groups ANOVA:
Beer Taste Testing
2. State null and research hypotheses
Null: People who drink cheap, mid-range, and high-end beer
rraattee tthheeiirr bbeeeerrss tthhee ssaammee, oonn aavveerraaggee.
Research: People who drink cheap, mid-range, and high-end
beer do not rate their beers the same, on average.