PSYCH 241 Lecture Notes - Lecture 6: Stroop Effect, Psych, Dependent And Independent Variables
18 Oct 2016
School
Department
Course
Professor
Psych 241 – Lecture 6
Repeated Measures Designs → within subject variables
• The same set of subjects serves at all levels of the IV
• Each subject is measured at each level of the IV
• The ultiate Mathed Groups desig – identical subs
• Example: the stroop task from lab
o Independent variable – presence of labels, or not (2 levels)
o Dependent variable – RT to name the animal silhouettes
o Design – 1 way with 2 levels, Repeated Measures design with incomplete
counterbalancing
• Why do we use Repeated Measures Designs?
o Conduct an experiment when few subjects are available
o Conduct the experiment more efficiently
o Increases the sensitivity of the experiment
o Can measure change in subjects over time (longitudinal studies)
• Perfectly matched subjects at each level of IV
o Secondary and Individual Difference variables balanced
• However, because subjects are measured repeatedly there are potential issues with co-
varying time-related variables (can pose serious threat to internal validity)
• Cooly alled pratie effets or order effets
• You aot eliiate order effets ut you a alae the aross levels of your IV
(counterbalancing)
• This can be done in several different ways and how you do this is tied to the type (name)
of counterbalancing you use: (Complete versus Incomplete counterbalancing)
• Complete – subjects in each condition multiple times
• Incomplete – subjects in each condition one time
o Balancing occurs when subjects are combined – all possible orders
Generic Example of Block Randomization
• Block Randomization
o Each block involves one occurrence of each level of the IV
o The order of the levels in each block is randomly assigned
• For example, IV with five levels: A, B, C, D, E
• One block would be a random order of the 5 levels
o BDACE could be one block, ECADB could be another
• Each subject would experience each level (A,B,C,D,E) 6 times
• How many data points would we have for each subject?
Research Example of Block Randomization
• Research Question: Does one side of our face express emotion more intensely than the
other?
• Hypothesis?
find more resources at oneclass.com
find more resources at oneclass.com
