Main Goal: Establish a cause-and-effect relationship between two variables.
Experiment Definition: A true experiment demonstrates that changes in one variable (Independent Variable - IV) directly cause changes in another variable (Dependent Variable - DV).
Causality Check: Rules out coincidental relationships.
Manipulation
The researcher alters one variable to create treatment conditions.
Measurement
A second variable is measured among participants, producing scores based on treatment conditions.
Comparison
Scores from one treatment condition are compared with another condition.
Control
Other extraneous variables are controlled to avoid influencing the examined variables.
Not specified in detail in this section but pertains to the infrastructure of conducting experiments effectively.
Independent Variable (IV): The manipulated variable with various treatment conditions.
Treatment Condition: A specific situation defined by the IV.
Levels: Different values of the IV used to define treatment conditions.
Dependent Variable (DV): The variable measured to assess effects of changes in the IV.
Extraneous Variables: All other variables in the study not classified as IVs or DVs.
Third Variable Problem: Establishes that two variables are related but may be influenced by an unidentified third variable which can cause a spurious relationship.
Directionality Problem: Not all studies clarify which variable is the cause and which is the effect.
Experiments must isolate examined variables from all other variables to clarify relationships and conclusions.
Ensure the IV precedes the DV.
Validate that a specific variable is the cause of changes in another variable, ruling out extraneous variables.
Manipulation Process: Determines specific IV values and creates corresponding treatment conditions.
Manipulation helps in identifying the direction of the relationship between IV and DV.
Example: Ice-cream consumption rises with temperature, but temperature does not change due to ice-cream distribution.
Manipulation helps control extraneous influences, like crime rates rising with temperature, showing no direct connection with ice-cream consumption.
Control other variables to prevent contamination of observed relationships and eliminate confounding variables (those varying with IV and DV).
A confounding variable can skew outcomes, causing misleading results by affecting the DV unintentionally.
An extraneous variable becomes confounding only if it influences the DV and varies systematically with the IV.
Holding Variables Constant: Ensures certain variables remain unchanged.
Matching Values: Ensures equal values across treatment conditions.
Randomization: Avoids systematic relationships by using random processes.
Goal: Ensure that differences in DV are caused solely by the IV, with no other variable influencing outcomes.
Holding Constant & Matching: Requires additional effort and measurement; can limit external validity.
Randomization: Controls multiple variables but may not succeed in balancing them effectively.
Experimental Condition: Represents treatment conditions.
Control Condition: Represents no-treatment conditions against which experimental conditions are compared.
No-treatment Control Condition: Does not receive the treatment but is crucial for comparison.
Placebo Control Condition: A non-effective treatment to assess psychological effects; known as the placebo effect.
Distinction between outcome research (effectiveness) and process research (active components).
Measures the effect of IV directly; executed through explicit measurements or participant questionnaires.
Important in varying situations such as participant manipulations, subtle manipulations, placebo controls, and simulations.
Simulation: Experimental conditions replicate natural environments.
Mundane Realism: Relates to real-life resemblance.
Experimental Realism: Refers to participant engagement.
Field Study: Conducted in natural settings as perceived by subjects.
Advantages: Increase external validity by investigating real-life situations.
Disadvantages: Risk of nature intruding, reducing control, potentially compromising internal validity.