Chapter 7 Flashcards
True Experiment
the independent variable must be under the control of the researcher.
Goal in conducting experiments
is to show that an IV causes a change in the DV.
quasi-experimental design
one that looks like a true experimental design but lacks the key ingredient – random assignment. Probably the most commonly used quasi-experimental design is the nonequivalent groups design.
In its simplest form it requires a pretest and posttest for a treated and comparison group.
It is nonequivalent because there is no random assignment
Advantages of Controlled Experiments Conducted in a Lab
Better control over the independent variable
Superior control over secondary or extraneous sources of variation
Can more precisely measure the DV
Improved internal validity
Disadvantages of Controlled Experiments Conducted in a Lab
Some phenomena can’t be studied in the lab
Some research topics present ethical problems
Practical disadvantages (e.g., costly, time consuming)
Outcomes may not be applicable to the real world (lack external validity)
Independent Group Design
Participants are randomly and independently assigned to each level of the independent variable.
Also known as between participants design.
Completely Randomized Group Design: One IV
Research participants are randomly assigned to different levels of one IV.
Simplest completely randomized design: two group design where participants are randomly assigned and independently assigned to either an experimental group or a control group (i.e., IV has two levels).
Can also use one IV with more than two levels
Randomized factorial groups designs: More than one IV
Participants are randomly assigned to each level of more than one IV (or factor).
Allow us to assess:
the effects of more than one IV on the DV (main effects)
the interaction between IVs (interaction effect)
The complexity of a factorial design increases with the number of levels of each variable and the number of IVs.
