Lecture 6: Experimental Research Flashcards
What is experimental research?
A research methodology where the researcher seeks to observe how changes in one or more variables impact on other variables.
It allows investigation of causal relationships.
Requires high levels of control.
What is an independent variable (IV)?
The variable that is manipulated (the assumed ‘cause’)
What is the dependent variable (DV)?
The outcome variable that is measured (the assumed ‘effect’)
What are extraneous variables?
Any other variables that impact on the relationship (e.g. ones that could weaken or distort results)
What are confounding variables (or confounds)?
A type of extraneous variable that systematically varies with the independent variable (i.e. one which might otherwise be responsible for the changes in the dependent variable)
What are controls?
When researchers aim to control or eliminate extraneous variables in the research design
What are some design issues?
Randomisation
- random assignment of participants and treatments to groups
- scatters extraneous variables between conditions
Matching
* assigning participants to conditions based on pertinent attributes
What are laboratory studies?
Experiment conducted in an artificial setting (such as a testing laboratory)
Researcher has much greater control over extraneous variables
What are field studies?
Experiment conducted in a natural setting
- difficult to control extraneous variables
- natural vs. formed conditions
What is a between-subjects design?
When comparisons are made between different groups of people
What is a within-subjects design?
When comparisons are made using the same group of people (e.g. with pre- and post- designs)
What is internal validity?
Whether variation in the DV can be confidently attributed to the variation in the IV
What is external validity?
The extent to which the results of can generalise beyond the current study.
- Is it likely that this group will also be found in non-experimental settings, with other groups, etc?
- Wider population?
What are the threats to internal validity? (7)
- Maturation effects
- Systematic changes in the participant across time points or within the course of a study
- Long-term maturation?
- Short-term maturation?
- History effects
- Where the participant’s environment has changed across studies or within the course of a study
- For example, brand crisis midway through longitudinal study
- Testing
- When an initial measure (e.g., pre-test) sensitises participants to the nature of the experiment
- Instrumentation
- Where changes in the measurement instrument change between test and re-test
- Selection
- Where participants are allocated to conditions in some systematic way
- Mortality (a.k.a. Attrition)
- Refers to participants dropping out of the study
- Problematic if there is systematic attrition
- Consider testing of social marketing programs on topics like safe sex, reduced speeding, quitting smoking
- Demand effects
- Where aspects of the experiment that provide cues to participants about researcher’s purpose, which are then acted upon by participants
- Hawthorne effect - unintended effects cause by participants behaving differently
What are maturation effects?
A threat to internal validity
- Systematic changes in the participant across time points or within the course of a study
- Long-term maturation?
- Short-term maturation?