exam 3 Flashcards
Criteria for cause
- Covariance - looking at changes in DV after manipulating IV
- Temporal precedence - manipulation of IV comes before change in DV
- Internal validity - manipulating IV while holding all other factors constant
Characteristics of experiments
- Empirical/objective approach - gathering information through the use of your five senses during systematic hypothesis testing
- Manipulation of variables - value of interest is manipulated and outcome is recorded
- Keeping other factors constant - consistent variation in all conditions
- Determining causal relationships
Independent variable MUST have…
-One IV in each experiment
-2 levels
-Can have more than one IV
-Can be discrete or continuous
Between subjects independent variable
different groups of subjects, different subjects in each level
Within subjects independent variable
Same subjects experience each level of IV
Types of manipulations
-Environmental - changing social or physical environment
-Instructional - changing instruction given to one group over another
-Invasive - create physical changes in participants
How to pick levels of IV
- trial and error - look at past research and choose ones that seem appropriate and hope for the best
- pilot study - pick levels that seem appropriate and try them out on a handful of participants
Manipulation check
institute measures within the study to determine if you actually manipulated what you think you did
Dependent variables must be
- reliable
- valid
- sensitive
- no ceiling/floor effects
Simple random assignment
every participant has an equal chance of being in each group. on average, groups should end up being equal in most characteristics
matched random assignment
matching people on a characteristic that is relevant to the experiment. requires a pretest and used when there is a possibility that random assignment will still cause inequalities between groups
advantages of within subject designs
-fewer participants are needed to detect differences
-more powerful
disadvantages of within-subjects designs
-order effects - practice effects- people improve b/c they have already done it before
-carryover effects - effects of condition A are still lingering when condition B begins
counterbalancing
presenting levels of the IV in different orders to different participants
threats to internal validity
- misc. design confounds - type of extraneous variable that varies systematically with the independent variable
- biased assignment to conditions
- differential attrition - people in one condition drop out at higher rate, no longer have random assignment
- pretest sensitization
- history - behavior is affected by a person’s past experiences
- maturation - developmental changes may take place and subjects behavior changes
one way experimental design
- contains only one IV
- simplest one way design: one IV two levels
- can be within or between subjects
factorial designs
-contains 2 or more IV
- designs can be between subjects, within subjects, or mixed