Experimental Research
An effect that is due to the placebo rather than the treatment
Placebo Effect
Studies that involve comparing two or more pre-existing groups of people
Cross-Sectional Studies
Major limitation to this design is the lack of a control or comparison group
One-Group Posttest Only Design
Shows how each level of one independent variable is combined with each level of the others to produce all possible combinations in a factorial design
Factorial Design Table
Part of a distribution that tapers at either direction from the peak
"Tails"
An experiment that researches the effectiveness of psychotherapies and medical treatments
Randomized Clinical Trial
A relationship in which higher scores on one variable tend to be associated with lower scores on the other
Negative Relationship
Similar to within-subjects experiment, however, the order of conditions is not counterbalanced
One-Group Pretest-Posttest Design
A design which manipulates one independent variable between subjects and another within subjects
Mixed Factorial Design
When a histogram's peak shifted toward the upper end of its range and has a relatively long negative tail
Negatively Skewed
An effect where participants perform a task worse in later conditions because they become tired or bored
Fatigue Effect
A statistical technique that allows researchers to predict the value of one variable given another
Regression
Refers to the statistical fact that an individual who scores extremely high or extremely low on a variable on one occasion will tend to score less extremely on the next occasion
Regression to the mean
The effect of one independent variable on the dependent variable—averaging across the levels of any other independent variable(s)
Main Effects
Represented by the symbol: H1
Alternative Hypothesis