Single Factor Experimental Designs
1. Single Factor – Two Levels: the simplest of all experimental designs; uses one IV which has two levels.
a. Between-Subjects, Single-Factor Designs – not very common; too simple
b. Within-Subjects, Single-Factor Designs – need to worry about counterbalancing:
- If subjects participate in each condition just once, COMPLETE counterbalancing will be used
- If subjects are tested more than once per condition:
- reverse counterbalancing will be used (ABBA)
- or we simply alternate the conditions (ABAB ...)
c. Analyzing Single-Factor, Two-Level Designs:
- t test for independent groups – (a) participants are randomly assigned to the groups or (b) the IV is a subject one (males vs. females)
- t test for dependent groups – within-subject design or matches groups.
2. Single Factor – More Than Two Levels: Most single-factor studies use three or more levels
a. Between-Subjects, Multilevel Designs -- A distinct advantage of multilevel designs is that they enable the researcher to discover NONLINEAR EFFECTS
b. Within-Subjects, Multilevel Designs – counterbalancing
c. Presenting the data
- Sentence (paragraph) form
- Table of results
- Graphs – bar graphs for nominal (discrete) data; line graphs for continuous data.
d. Analyzing Single-Factor, Multilevel Designs -- ANOVA