Research Design and Methods
Variables and Effects
Sampling Methods
Validity and probability
Bias and logical fallacies
100
Experiment
A controlled test or investigation, designed to examine the validity of a hypothesis. Also, the act of conducting an investigation.
100
Independent variable
The variable that is manipulated in an experiment.
100
Population
The group of individuals being studied.
100
Causation
When one variable causes the other.
100
Confirmation bias
The tendency to interpret evidence as confirmation of one's preexisting beliefs.
200
Single-blinded study
An experimental procedure in which the participants do not know whether they have received the treatment being tested.
200
Dependent variable
The variable that is observed and measured and that may change as a result of manipulations to the independent variable.
200
Sample
A subset of individuals in the population.
200
Correlation
A complementary, parallel, or reciprocal relationship between two variables.
200
Sampling bias
The tendency for some members of the population to be over-represented and others to be excluded from a sample.
300
Double blinded study
An experimental procedure in which neither the investigator nor the participants know who is in the experimental group and who is in the control group.
300
Placebo
A substance or procedure that has no therapeutic effect and may be used as a control in experimental research designs or to reinforce a patient's expectation of recovery.
300
Simple random sample
A sample in which each member of the population has an equal probability of participating.
300
Validity
An indication of how reliable the research is.
300
Volunteer bias
The tendency for those who volunteer for research to be different in some way from those who refuse to participate
400
Longitudinal study
The same group of participants is observed, measured, or tested over time.
400
Expectancy effect
An effect that may occur when a research participant's expectation of a certain result affects the outcome of the experiment.
400
Representative sample
A sample that has similar characteristics (such as age, gender, ethnicity, education) as the population from which it was drawn.
400
External Validity
The degree to which the findings can be applied in other settings.
400
Fallacy of insufficient evidence
An argument that does not provide sufficient evidence to support the conclusion.
500
Cross-sectional study
Surveys that obtain data from respondents at one point in time; cannot be used to examine trends over a longer period of time.
500
Confounding factor
A variable that is not the focus of the experiment, but which changes along with the independent variable, making it difficult to determine causal factors underlying the result.
500
Convenience sample
A sample that is not necessarily representative of the population, but that is easily accessible to the researcher.
500
Internal validity
The degree to which an experiment avoids confounding factors.
500
Fallacy of relevance
An argument that is irrelevant to the matter at hand.