Class Notes (865,646)
CA (523,043)
Western (51,171)
Psychology (6,376)
2800E (123)
Lecture 16

Lecture 16 - Factorial Experiments.docx

5 Pages

Course Code
Psychology 2800E
Doug Hazlewood

This preview shows pages 1 and half of page 2. Sign up to view the full 5 pages of the document.
Factorial Experiments - “Multiple factor experiments” - Experiments with more than one independent variable (or “factor”) - Allow us to study the effects of more than one “cause” Part 1: The Notation System  - 3 basic features: o Each factor (IV) is identified by a number o The numerical values indicate the ”levels” of each factor (e.g., “2” = 2 levels) o Create all possible combinations of levels by “crossing” each factor (symbol = “x” = “by”)  Each unique combination of factors and levels defines a “condition”  Number of conditions = product of levels (multiply the levels of each factor) - Examples: 1. 2x2 factorial (simplest design) o Two factors (IV’s) o Each factor has two levels – if it doesn’t have 2 levels, there’s no variability  4 conditions (2x2=4) 2. 3x3 factorial o Two factors (IV’s); each factor has 3 levels  9 conditions (3x3=9) 3. 2x3x2 factorial o Three factors, with 2, 3, and 2 levels  12 conditions (2x3x2=12) - Note typo on p.284 (W&M): A 3x3x3 factorial has 27 conditions, not 9 - It’s possible to have any number of factors (with any number of levels): 2x4x3x7… - BUT, as design becomes more complex, it’s more difficult to interpret the results o Limit the number of factors/levels to address the specific questions that you want to answer o Science grows by examining a few causes at a time Part 2: The “Factorial Cell Matrix” Notation System - Assign a capital letter to each factor (A, B…) - Assign numerical subscripts to represent the levels of each factor (e.g., A1, A2…) o Numbers should preserve “quantity” (e.g., low = 1; high = 2) o If categorical, numbers are arbitrary (e.g., gender: M = 1, F = 2 or F = 1, M = 2) - Create factorial matrix that represents all combinations of factors/levels o Each “cell” represents a condition - Example: 2x2 Factorial Factor A A1 A 2 Factor B B 1 A1B1 A 2 1 B 2 A1B2 A 2 2 - Concrete Example: 2x2 factorial (p. 274) - DV = judged “guilt” of defendant - Factor A: facial expression o A1 = “neutral” o A2 = “smiling” - Factor B: physical attractiveness o B1 = unattractive o B2 = attractive - Note: This design could be expanded to include: 1. A third level of each factor. E.g., o neutral (A1); small smile (A2); big smile (A3) o unattractive (B1); neutral (B2); unattractive (B3) 2. More than two factors (IV’s). E.g., o Gender of def (C1 = male; C2 = female) o Trust (D1 = untrustworthy; D2 = trustworthy) o 3x3x2x2 =36 conditions - Remember, more factors = more complexity (or more possible outcomes) Part 3: Outcomes of Factorial Experiments A. Main effects: allow us to examine the separate effects of each factor - Easy to examine main effects by focusing on “marginal means” in matrix (e.g., 2x2) o Main effect of A (column means, p. 274); table 11.4 p274 W&M  Compare A1 (averaged over B1 and B2) and A2 (averaged over B1 and B2) o Main effect of B (ro
More Less
Unlock Document
Subscribers Only

Only pages 1 and half of page 2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
Subscribers Only
You're Reading a Preview

Unlock to view full version

Unlock Document
Subscribers Only

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.