1. CHOOSING A RESEARCH DESIGN
CHAPTER 6
CHOOSING A RESEARCH DESIGN

2. DESIGNING A STUDY TO ANSWER A QUESTION
The type of study you conduct depends on the type of question you are asking
Research design – Specific methods and procedures used to answer a research question
A set of rules indicating how to collect observations
Types of research questions are categorized as exploratory, descriptive, or relational

3. DESIGNING A STUDY TO ANSWER A QUESTION

4. CATEGORIES OF RESEARCH DESIGN
Distinguished by the level of control established in the design
Control: Used to describe (a) the manipulation of a variable and (b) holding all other variables constan

5. Is experimental control a good thing?

6. How do we make out blurred images?
Experiment 1
Experiment 2
Selected images from web
Photoshop: “Gaussian blur”
Data collection online, participation from home
“vetted” images
Matlab: extract spatial frequencies
Data collection in-person, fixed distance from monitor (chin rest), calibrated light intensity, lighting in room, size of monitor
Full vision screening

7. CATEGORIES OF RESEARCH DESIGN
Non-experimental research design – Use of methods and procedures to make observations in which the behavior or event is observed “as is” or without an intervention from the researcher
Strength: Can be used to make observations in settings that the behaviors and events being observed naturally operate
Limitation: Lacks control needed to demonstrate cause and effect

8. CATEGORIES OF RESEARCH DESIGN

9. CATEGORIES OF RESEARCH DESIGN
Experimental research design – Use of methods and procedures to make observations in which the researcher fully controls the conditions and experiences of participants. Used to make causal inferences.
Required elements of control: Randomization
Random sampling: Select a sample at random
Random assignment: Assign to group at random
Individual differences: Unique characteristics of participants in a sample that can differ from one participant to another
Confound or confound variable: Unanticipated variable not accounted for in a research study that could be causing or associated with observed change in one or more measured variables (vs extraneous variable)
Strength: Capable of demonstrating cause and effect
Limitation: Behavior that occurs under controlled conditions may not be the same as behavior that occurs in a natural environment

10. DEMONSTRATING CAUSE IN AN EXPERIMENT
Independent variable (IV) or factor: The variable that is manipulated. It is the “presumed cause”
Level: Specific conditions or groups created by manipulating that factor
Dependent variable (DV): Variable that is believed to change in the presence of the IV. It is the “presumed effect”

12. Demonstrating Cause in an Experiment
Laboratory experiment – Takes place in a laboratory setting in which the researcher has greatest control over variables, regardless of whether it is made to look natural or not
Field experiment – Takes place in an environment within which the behavior or event being observed would naturally operate

14. Implicit Association Test : http://implicit.harvard.edu

15. CATEGORIES OF RESEARCH DESIGN
Quasi-experimental research design – Use of methods and procedures to make observations in a study that is structured similar to an experiment, but the conditions and experiences of participants lack some control (no random assignment)
Quasi-independent variable: Any factor in which the levels of that factor are preexisting
Examples: smoking and pregnancy, autism & vaccines, gender, mental health status
Strength: Allows researchers to study factors related to the unique characteristics of participants
Limitation: Cannot demonstrate cause and effect

16. INTERNAL AND EXTERNAL VALIDITY
Internal validity – Extent to which a research design includes enough control of the conditions and experiences of participants that it can demonstrate a single unambiguous explanation for a manipulation, that is cause and effect
External validity – Extent to which observations made in a study generalize beyond the specific manipulations or constraints in the study
Constraint: Any aspect of the research design that can limit observations to the specific conditions or manipulations in a study

17. ETHICS IN FOCUS: BENEFICENCE AND RANDOM ASSIGNMENT
Random assignment ensures that all participants have an equal chance of being assigned to a group and receiving whatever benefits and costs that are associated with that group
May not be sufficient when one group has obviously greater benefits than another group
Researchers often compensate the disadvantaged group, referred to as compensatory equalization of treatments
This is provided in order to meet the ethical standard of beneficence, as required by the APA code of conduct
Beneficence: Equal distribution of potential costs and benefits of participation

18. Threats to the Internal Validity of a Research Study
Instrumentation and measurement – Measurement of the DV changes due to an error during the course of a research study
Attrition or experimental mortality – Participant does not show up for a study at scheduled time or fails to complete the study
Environmental factors – Characteristics of the study itself and the actions of the researchers
Can only threaten internal validity when it varies systematically with the levels of an IV
Test all of your participants in the same place if you can help it!

19. THREATS TO THE INTERNAL VALIDITY OF A RESEARCH STUDY (quasi-experimental designs)
History effects – An unanticipated event that co-occurs with a treatment or manipulation in a study (Sesame Street and the Head Start Program)—only relevant to single-group pre-post
Maturation – A participant’s physiological or psychological state changes over time during a study
Regression toward the mean – Change or shift in a participant’s performance toward a level or score that is closer to or more typical of true potential or mean ability on some measure, after previously scoring unusually high or low on the same measure (often when selection is biased)
Testing effects – The improved performance on a test or measure the second time it is taken due to the experience of taking a test

20. Threats to the External Validity of a Research Study
Population validity – Extent to which results observed in a study will generalize to the population from which a sample was selected
Homogeneous attrition: Rates of attrition are about the same in each group
Ecological validity – Extent to which results observed in a study will generalize across settings or environments
Temporal validity – Extent to which results observed in a study will generalize across time and at different points in time
Outcome validity – Extent to which results observed in a study will generalize across different but related DVs

21. External Validity, Experimentation, and Realism
Mundane realism – Extent to which a research setting physically resembles or looks like the natural or real-world environment being stimulated
Experimental realism – Extent to which the psychological aspects of a research setting are meaningful or feel real to participants
To enhance this, it is important that the manipulations are meaningful to participants
Increasing mundane and experimental realism will increase the external validity of a research result