Week 8: Experimental and Quasi-Experimental Research Methods Flashcards
What is the experimental research strategy (aka experimental method)?
One variable is manipulated while another variable is observed and measured. To establish a cause-and-effect relationship between the two variables, an experiment attempts to control all other variables to prevent them from influencing the results.
What is an experiment?
Attempts to show that changing the value of one variable causes changes to occur in the second variable.
What are the two characteristics in the experimental method that differentiate experiments from other types of research studies?
Manipulation and Control
What is manipulation?
The researcher manipulates one variable by changing its value from one level to another. In the Polman et al. (2008) experiment examining the effect of violence in video games (Figure 1.5), the researchers manipulate the amount of violence by giving one group of boys a violent game to play and giving the other group a nonviolent game. A second variable is observed (measured) to determine whether the manipulation causes changes to occur.
What is control?
The researcher must exercise control over the research situation to ensure that other, extraneous variables do not influence the relationship being examined.
What are the two general categories of variables that researchers must consider?
Participant Variables and Environmental Variables
What are the three basic techniques researchers typically use to control other variables?
- Random assignment (equal chance of being assigned to a group) 2. Matching (e.g ensuring every group holds exactly 60% females and 40% males) 3. Holding them constant (e.g just using 10 year olds in the study)
True or false: in an experiment BOTH variables are measured?
FALSE. Only one is measured - the Dependent variable. The Independent variable is manipulated by the researcher.
What is the difference between a correlation study and an experimental study regarding variables?
In a correlation study, BOTH variables are measured (we obtain data consisting of two separate scores), where as in an experimental study, only the dependent variable is measured.
What is the control condition?
Individuals in a control condition do not receive the experimental treatment. Instead, they either receive no treatment or they receive a neutral, placebo treat-ment. The purpose of a control condition is to provide a baseline for comparison with the experimental condition
What is the experimental condition?
Individuals in the experimental condition do receive the experimental treatment.
The independent variable has to have at least ___ values (groups or conditions) to be considered a “variable”?
TWO
What is a “between-subjects” design?
An experiment in which different subjects are assigned to each group.
The control group is the group that serves as the ____?
Baseline, or “standard” condition
The experimental group is the group that receives some level of the ____?
Independent Variable
We describe the two groups in an experiment as the ______ and _____ groups?
Experimental and Control
True or false: an experiment may involve the use of two experimental groups and no control group
TRUE.
How do we control who is in the study?
By (ideally) random sampling, to gather a sample that is representative of the population about whom we are trying to generalize. Further, use random assignment of subjects to two conditions (to make groups equivalent)
What are the two major problems with successfully conducting an experiment PROVING there is a causal relationship between smoking and cancer?
Firstly, it is completely unethical to assign participants to the experimental group by which they smoke for a period of time Secondly, in order for the experiment to be successful we would have to control many other aspects of their life for the period of time needed to conduct the study.
What is the posttest-only control group design?
An experimental design in which the dependent variable is measured after the manipulation of the independent variable.
What is a pretest/posttest control group design?
An experimental design in which the dependent variable is measured both before and after manipulation of the independent variable.
How many subjects per condition is considered adequate?
20 to 30 subjects per condition
What are the disadvantages of multiple testings?
There is more opportunity for an experimenter to influence the subjects.
What is a Solomon four-group design?
A design with four groups that is a combination of the posttest only control group design and the pretest/posttest control group design. By merging the two designs, the disadvantages of each individual design are minimized, and the advantages are maximised.
If a researcher fails to control for something, then the study is open to ____?
Confounds
What are confounds?
An uncontrolled extraneous variable or flaw in an experiment.
What are the problems with confounds in an experiment?
If a study is confounded, it is impossible to say whether changes in the dependent variable were caused by the independent variable or by the uncontrolled extraneous variable.
Why is maximising control with human subjects so difficult for psychologists?
Because humans have many dimensions - personality, intelligence, rearing issues. There is great variability, so psychologists need to be concerned about preexisting differences.
To avoid extraneous variables, we need to maximise the ____ validity of a study?
Internal
What is the “internal validity”?
The extent to which the results of an experiment can be attributed to the manipulation of the independent variable rather than to some confounding variable.
What are the threats to internal validity?
Nonequivalent Control Group (when random sampling and random assignment are not used - may lead to important differences between the subjects assigned to the experimental and control groups) History effect Maturation Testing effect Regression to the mean Instrumentation effect Mortality (attrition) Diffusion of treatment Experimenter Effect
Confounds are most problematic to _____ designs?
Nonexperimental
What is the history effect?
Changes in the dependent variable may be due to outside events that take place during the course of the study. To minimise, use an equivalent control group.
What is the maturation effect?
Changes in the dependent variable may be due to subjects maturing (growing older) during the course of the study. To minimise, use an equivalent control group.
What is the testing effect?
Changes in the dependent variable may be due to participants being tested repeatedly and getting either better or worse because of these repeated testings. To minimise, use an equivalent control group.
What is the regression to the mean?
Subjects who are selected for a study because they are extreme (either high or low) on some variable may regress toward the mean and be less extreme at a later testing. To minimise, use an equivalent group of subjects with extreme scores.
What is the instrumentation effect?
Changes in the dependent variable may be due to changes in the measuring device, either human or machine. (particularly problematic when humans are the measurement device - ie qualitative research - perhaps human is fatigued) To minimise, use an equivalent control group.
What is mortality (attrition)?
Differential attrition or dropout in the experimental and control groups may lead to inequality between the groups. To minimise, monitor for differential loss of subjects in experimental and control groups.
What is diffusion of treatment?
Changes in the behaviors or responses of participants may be due to information they have received from others participating in the study. e.g students talking to other students about the study, effecting the study To minimize, test subjects all at once or as close together in time as possible.
