dependent variable
What is measured. It is what is affected by manipulation of the independent variable
Independent variable
The treatment measure - what is manipulated by the experimenter.
Cause-effect relationships
Can be found by experiments
Cross-sectional research
measures people from various age groups simultaneously
Ex Post Facto studies
(Retrospective / causal-comparative studies)
The independent variable (I e., # siblings, SES; # cigarettes) known. Start with effect and seek causes; no random assignment
Solomon Four-Group Design
With two control groups and two experimental groups. Half the groups have a pretest and half do not have a pretest. This tests both the effect itself and the effect of the pretest.
Between Subjects Design
Grouping Participants to Different Conditions
Within Subject Design
Participants Take Part in the Different Conditions - Also: Repeated Measures Design
Counterbalanced Measures Design
Testing the effect of the order of treatments when no control group is available/ethical
Matched subjects design
Matching participants to create similar experimental- and control-groups
Double-Blind Experiment
Neither the researcher, nor the participants, know which is the control group. The results can be affected if the researcher or participants know this.
Bayesian Probability
Using bayesian probability to interact with participants is a more dvanced experimental design. It can be used for settings were there are many variables which are hard to isolate. The researcher starts with a set of initial beliefs, and tries to adjust them to how participants have responded
Nominal Variables
Category or name
i.e. Girls / Boys
Ordinal Variables
Rank or ordering of levels
- Likert Scale
Interval Variables
Numerical with equal intervals or distance between numbers
- Scores on an exam
Ratio Variables
Same as interval scale but there is an absolute zero indicating an absence of the property measured
- i.e. Syllables stuttered
Single-Subject Designs
- Help establish efficacy of treatment procedures and cause-effect relations
- Dependent variables are measured continuously and results don’t require statistical analysis
- Types include AB, ABA, ABAB, and multiple-baseline design
A= skills measured without treatment or when withdrawn
B= skills taught and results measured
Multiple-Baseline Designs
- A multiple baseline design can be across subjects so it includes several subjects who are taught one or more behaviors in a staggered way to show that only the behaviors of treated participants change.
- A multiple baseline design can also be across settings
- Collect base rates in 3 or more settings, teach behavior in one setting, repeat assessing in untreated settings then teach behavior in another setting. Teach in different settings until behavior is trained in all settings.
Group Designs
- Experimental or nonexperimental
- True experimental research helps rule out effects of confounding variables by using randomization and a control group
- Within subjects designs have one group
- Between subjects designs have two+ groups
- Pretest-Posttest Control Group Design
Validity in Research
Degree to which an instrument measures what it intends to measure
- Content validity
- Criterion-related validity
- Concurrent validity
- Predictive validity
- Construct validity
8 Internal Validity Issues
Internally valid findings must reflect true cause-effect
- Instrumentation – measurement devices
- History – life events responsible for changes
- Statistical regression – behavior that is at poles (high or low) moves toward mean
- Maturation – unexpected biological changes in participants
- Attrition – mortality and drop-out rate
- Testing – repeated measurement
- Subject selection bias – factors influencing initial selection
- Interaction of factors – combination of above
3 External Validity Issues
Externally valid findings must have generalizability
- Hawthorne Effect – study’s results affected by fact that people know they are taking part in an experiment
- Multiple-Treatment Interference – can be a concern when 2+ treatments are administered to the same person; order effects can also be a concern
- Reactive or Interactive Effects of Pretesting – may be a problem if the pretest measure is also the dependent variable
- for example, a vocal hygiene questionnaire is given to a control group subject who then tries to modify his vocal abuse
Reliability in Research
Consistency with which something is measured on repeated occasions
- Test-retest reliability
- Alternate-form reliability
- Split-half reliability
- Interobserver / interjudge reliability
- Intraobserver or intrajudge reliability
Inductive method
Specific to general
- Conclusion based on patterns that you see.
- Experiment first and draw conclusion next.
EXAMPLE: What is the next number in the sequence 6, 13, 20, 27
