Lecture 6 Flashcards
Causality
a change in the dependent variable is the consequence of the independent variable (keeping all other things equal)
Classic experimental design
Random assignment, Compare T1 and T2 in experimental condition and control condition
Control group/condition
group in which variables that also occur in the experimental group/condition are kept the same (ceteris paribus), except the variable of interest
Random assignment to conditions
Each subject has an equal probability to be assigned to one or the other group/condition
- Neutralizes the effect of individual factors (e.g., personal experience, individual traits, severity of symptoms). Thus, counters threats to internal validity by selection
Quasi-experiments
Studies that have characteristics of experimental designs but do not fulfill all requirements
Non-equivalent control group design
experimental and comparison groups are designated before the treatment occurs, but not by random assignment
Ex post facto control group design
Non-experimental design in which participants can choose the group in which they participated
Before-and-after designs
A quasi-experimental design consisting of a beforeafter comparison, but no comparison (control group).
Dependent variable (dv)
the outcome variable, what is measured, the variable on which you monitor an effect
Independent variable (iv)
the variable you can control, manipulate or choose and that may have causal impact
Between subjects variable
Every participant gets a different manipulation
manipulation check
you can check whether the concept was successfully manipulated
Within subjects variable
every participant gets all different manipulations
Stimuli
can be presented randomly or counterbalanced
Counterbalancing
Vary the order of within manipulations to counter order effects.
Complex designs
- Experimental designs can combine multiple (within & between!) independent variables
- Experimental designs can combine manipulable and nonmanipulable independent variables
Deception
Researchers sometimes deceive participants about:
- the truth of a manipulation
- the goal of the study
Coverstory
informing the participant about a fictional goal of the study, to conceal the true goal of the study
Laboratory experiments
Controllable, thus:
- practical for random assignment
- practical for the implementation of your independent variable
- easier to replicate
Disadvantages of experiments
- Lack of external validity
- Lack of ecological validity
Pitfalls
- Bias through demand characteristics
- Experimenter bias
Nudging
little “push” towards certain behaviour based on insights from psychology and behavioural economics.
