Variable
- Any event, situation, behavior, or individual characteristic that varies
- Any variable must have two or more levels of values
- Four General Categories of Variables:
- Situational variables
- Response variables
- Participant or subject variables
- Medi
Mediating variable
- the variable that causes mediation in the dependent and the independent variables. In other words, it explains the relationship between the dependent variable and the independent variable.
Operational definition
- the set of procedures used to measure or manipulate it
- Variable is an abstract concept that must be translated into concrete forms of observation or manipulation
- Studied empirically
- Help communicate ideas to others
Wong-Baker FACES Pain Rating Scale
- Used for a child
Construct validity
- Concerns whether our methods of studying variables are accurate
- Refers to the adequacy of the operational definition of variables:
- Does the operational definition of a variable actually reflect the true theoretical meaning of the variable?
Relationships between variables
- Positive Linear Relationship
- Negative Linear Relationship
- Curvilinear Relationship
- No Relationship
Positive Linear Relationship
- Increases in one variable relate to increases in another
Negative Linear Relationship (Inverse relationship)
- Increases in one variable relative to decreases in another
Curvilinear Relationship
- Increases in one variable relative to both increases and decreases in
another
- Included U-shaped and Inverted U-shaped curves
- Sometimes referred to as a "nonmonotonic function
No Relationship
r = 0
Correlation coefficient
- A numerical index of the strength of relationship between variables
- r cannot be less than 0, more than 1 (+ or - just tell us direction)
- Interpretation of whether r is strong, mediate, or weak depends on each data
Random variability
- Uncertainty
- Randomness in events
- Research is aimed at reducing random variability by identifying systematic relationships between variables
- e.g. Some people like to shop and others do not
Nonexperimental method
- Relationships are studied by making observations or measures of the variables of interest
- Direction of Cause and Effect Problem
- The Third-Variable or Confounding Variable Problem
- Must not determine about cause and effect
Experimental method
- Experimental Control (manipulation of variables)
- Randomization
Direction of Cause and Effect
- With nonexperimental method, it is difficult to determine which variable causes the other (e.g. coffee ? Anxiety? OR anxiety ? coffee?)
Third variable problem
- There may be a relationship between the two variable because SOME OTHER variable causes both variables
- A third variable is any variable that is extraneous to the two variables being studied
- "Spurious relationship
Confounding variable
- A third variable that is not controlled in a research investigation
- In an experiment, the experimental groups differ on both the independent variable and the confounding variable
Experimental control
- Eliminating the influence of an extraneous variable on the outcome of an experiment by keeping the variable constant in the experimental and control groups
- Only difference between groups should be the manipulated variable (IV)
Randomization
- Controlling for the effects of extraneous variables by ensuring that the variables operate in a manner determined entirely by chance
- In case of participants arriving for the experiment at various times during several days or weeks, the researcher uses
Independent variable
- The variables that are considered to be the "cause"
- Usually MANIPULATED by the researcher
Dependent variable
- The variables that are considered to be the "effect"
- Usually MEASURED by the researcher
Causality
- Inferences of Cause and Effect Require Three Elements:
1. Temporal precedence
2. Covariation between the two variables
3. Need to eliminate plausible alternative explanations
Internal validity
- Refers to the accuracy of conclusion about cause and effect
- Ability to draw conclusions about causal relationships from our data
- A study has high internal validity when strong inferences can be made that one variable caused changes in the other vari
External Validity
- Concerns whether we can generalize the findings of a study to other settings
- Extent to which the results can be generalized to
other populations and settings
- Stronger the internal validity, weaker the external validity (less likely to happen in gene
Conclusion validity
- Draws reasonable conclusions based upon an analysis of the data
Choosing a method
- Artificiality of Experiments
- Ethical and Practical Considerations
- Participant Variables
- Description of Behavior
- Successful Predictions of Future Behavior
- Advantages of Multiple Methods
Artificiality of experiments
- IV is manipulated within the carefully controlled confines of a laboratory
- This procedure permits relatively unambiguous inferences (strong internal validity) concerning cause and effect and reduces the possibility that extraneous variable could influ
Field experiment
- An experiment that is conducted in a natural setting rather than in a laboratory setting
- IV is manipulated in a natural setting
- A confederate may create IV (situation)
Ethical and Practical Considerations
- Sometimes the experimental method is not a feasible alternative because experimentation would be either unethical or impractical
- e.g. Child-rearing,
- "ex post facto
Ex post facto design
- "after the fact"
- Groups are formed on the basis of some actual difference rather than through random assignment as in an experiment
Participant Variables (subject variables; personal attributes)
- Characteristics of individuals, such as age, gender, ethnic group, nationality, birth order, personality, or marital status
Advantages of multiple methods
- Complete understanding of any phenomenon requires study using multiple methods, both experimental and nonexperimental.