Introduction to Experimental Research Flashcards
Independent variable
the variable being controlled/ manipulated by the researcher
Extraneous variables
variables that are not of interest to the researcher so they must be held constant as to not influence results
Dependent variable
behaviours being measured
All manipulated independent variables must have a minimum of ___ levels
two
Ex; two dosage levels of caffeine in order to make a comparison between the effects of caffeine and reaction time
Independent variables that are manipulated in a study tend to fall into three somewhat overlapping categories:
- Situational
- Task
- Instructional
Situational variables
Features in the environment that participants might encounter
Ex; in a helping behaviour study, the researcher interested in studying the effect of the number of bystanders on the chances of help being offered might create a situation in which subjects encounter a person in need of help
Task variables
Problems to solve
Ex; research on the psychology of reasoning often involves giving people different kinds of logic problems
Instructional variables
Manipulated by telling different groups to perform a particular task in different ways
Ex; students in a memory task who are all shown the same list of words might be given different instructions about how to memorize the list
Confound
Any uncontrolled extraneous variable that co-varies with the independent variable
Two major problems that can occur with poorly chosen dependent variables:
- Ceiling effect
2. Floor effect
Ceiling effect
When the average scores for the groups in the study are so high that no difference can be determined between conditions
This can happen when your dependent measure is so easy that everyone gets a high score
Floor effect
Happens when all the scores are extremely low
This usually happens because the task is too difficult for everyone
Subject variables
Already existing characteristics of the individuals participating in the study (age, gender, SES)
To judge whether change occurred one procedure is to evaluate people prior to the experience with a _______ then follow with a _____
pretest, posttest
Regression to the mean
Refers to the fact that if the first score from a subject is an extreme score, then the second or third score from the same person will be closer to whatever the mean is for the larger set of scores
Attrition
Participants don’t always complete the experiment they begin
Why is attrition a problem?
If particular types of people are more likely to drop out than others, then the group finishing the study is made up of different types of people than the group that started
The X is what Woodworth called the _________ ________
independent variable
The independent variable is sometimes called the __________ variable
manipulated
Statistical conclusion validity
the extent to which the researcher uses statistics properly to draw an appropriate conclusion
If the dependent measures are not reliable, there will be a great deal of error validity. What type of error would occur?
Type II error
Construct validity
Whether a test truly measures some construct and thus refers to the adequacy of operational definitions
External validity
Degree to which research findings generalize beyond the laboratory (to other populations, to other environments, and to other times)
Ecological validity
Subtype of external validity. Degree to which research findings can be generalized to real life settings
Internal validity
Degree to which an experiment is methodologically sound and confound-free
3 threats to internal validity
- History and maturation
- Regression to the mean
- Testing and instrumentation
