1. Questions
I have had some professors who have a preference on APA style, is the library website a good source for APA format? Do you have a particular preference?
What are the consequences if a researcher does not behave ethically towards individuals?
How do you determine the sample size in a given research study?
How do you know whether or not the chosen sample is representative of the target population?

2. More Questions
How do you know if you are inflicting any psychological harm on subjects in animal research? (such as in a controlled lab experiment and not just in observation).
In the abstract of a research report, do you need to separate the sections into background, methods, results, conclusions or can you make it one paragraph?
If a research has to ethically release all information to a participant before an experiment, how can you ethically run a double blind study where the participant has no idea what is being done.

3. More Questions
How can the way in which results are reported become an ‘ethical issue’ of the research process?
To do a research, you have to take the Ethics code test. Do you have to retake the test for every research study/experiment that you do or do you only have to take it once?

4. Research strategies and validity
Chapter 6
Dusana Rybarova
Psyc 290B
May

5. Outline Introduction to research strategies Validity and its threats
- internal validity
- external validity
Research strategies, research designs and research procedures

6. 1. Introduction to research strategies
research strategy
reflects the general approach and goals of a research study
types of research strategies
descriptive strategy
Nonexperimental strategy
correlational strategy
experimental strategy
quasi-experimental strategy

7. 1. Introduction to research strategies
Descriptive strategy
the goal is to describe the state of affairs at the time of the study
measures variables as they exist naturally
e.g. 19% of eligible voters participated in the election
Correlational strategy
measures two variables, usually as they exist naturally
the goal of this strategy is to describe a relationship between the two variables without attempting to explain the cause of the relationship
e.g. Are students GPA’s related to their parent’s income?
Nonexperimental strategy
Answers questions about the relationship between two variables by demonstrating a difference between two groups or two threatment conditions
E.g. verbal scores of 6-years old boy and 6-years old girls

8. 1. Introduction to research strategies
Experimental strategy
the researcher manipulates one variable (called independent variable) while observing or measuring a second variable (dependent variable)
this is the ‘true’ experiment because independent variable is manipulated by the researcher (e.g. room temperature)
the goal of experimental strategy is to determine whether a causal relationship exists between two variables

9. 1. Introduction to research strategies
Quasi-experimental strategy
uses a nonmanipulated variable to define groups or conditions (e.g. time or age) or pre and post threatment
controls other variables as much as possible
the goal is to obtain evidence in support of a cause-and-effect relationship
however, a quasi-experimental strategy can not unambiguously establish a causal relationship

10. 2. Validity and its threats
validity is the standard criterion by which researchers judge the quality of research
in this case the concept of validity applies to an entire research study
any component of a research study that introduces questions or raises doubts about the quality of the research process or the accuracy of the research results is a threat to validity

11. 2. Validity and its threats
Internal validity
is concerned with factors within the research study that raise doubts about the results or the interpretation
any factor within the study that allows an alternative explanation for the results is a threat to internal validity
e.g. example with room temperature and performance

12. 2. Validity and its threats
threats to internal validity
Extraneous variables
any variable in a research study other than the two variables being studied (both systematic and unsystematic)
unsystematically changing variables are usually not a problem
confounding variable is an extraneous variable that is allowed to change systematically along with the two variables being studied (e.g. time of the day in the temperature-performance study)

13. 2. Validity and its threats
threats to internal validity
sources of extraneous/confounding variables
participant variables
assignment bias – when the process used to assign different participants to different threatments produces groups of individuals with noticeably different characteristics (e.g. one group is smarter, more motivated)
environmental variables
size of room, time of day, or gender of the experimenter
measurement variables
practice effects – prior exposure to a measurement procedure provides participants with additional skills that produce improved scores (e.g. the same exam)
fatigue – prior participation tires the participants so that their scores on subsequent measurements are lower

14. 2. Validity and its threats
External validity
concerns the extent to which the results obtained in a research study hold true outside the constraints of the study
Can the results be generalized to other populations, other settings, other measurements?
e.g. can we generalize results from a well-controlled laboratory situation to the uncontrolled chaos of the real world?

15. 2. Validity and its threats
threats to external validity
Participants
characteristics unique to a specific group of participants in a study may limit ability to generalize the results to individuals with different characteristics
e.g. college students, volunteer bias, cross-species generalizations
Features of the study
characteristics unique to the specific procedures used in a study may limit ability to generalize the results to situations where other procedures are used
e.g. novelty effect, reactivity, specifics of the study (masking experiments, lexical decisions)

16. 2. Validity and its threats
threats to external validity
experimenters
characteristics unique to the specific experimenter conducting the study may limit ability to generalize the results to situations with a different experimenter
e.g. experimenter bias, experimenter characteristics
measurements
characteristics unique to the specific measurement procedure may limit ability to generalize the results to situations where a different measurement procedure is used
e.g. sensitization (the impact of being assessed), generality across different measures (heart beat vs. questionnaire), time of measurement

17. 2. Validity and its threats
Balancing internal and external validity
attempts to increase internal validity can reduce external validity (laboratory experiments)
research that attempts to gain a high level of external validity will often create a research environment that closely resembles the outside world
there tends to be a tradeoff between internal and external validity (if you increase internal validity, external validity decreases a vice versa)

18. 2. Validity and its threats
Validity of individual research strategies
descriptive strategy
high external validity
low internal validity
Nonexperimental strategy
High external validity
Low internal validity
correlational strategy

19. 2. Validity and its threats
Validity of individual research strategies
experimental strategy
high internal validity
low external validity
quasi-experimental strategy
higher internal validity than descriptive and correlational studies
lower internal validity than true experiments
relatively high external validity

20. 3. Research strategies, research designs, and research procedures
Research strategy
refers to the general approach and goals of the study
Research design
general plan for implementing a research strategy (e.g. group versus individual, same individuals vs. different individuals, number of variables included)
Research procedure
an exact, step-by-step description of a specific research study (exact involvement of individuals, measurement of variables etc.)