CRIM 220 - Lecture 5 - Experimental Designs

Independent Variable

The ‘cause’ in an experiment that is manipulated to observe its effects on the dependent variable.

Dependent Variable

The ‘effect’ in an experiment that is measured to assess the impact of the independent variable.

Pretesting

Measuring the dependent variable before exposure to the independent variable.

Posttesting

Measuring the dependent variable after exposure to the independent variable.

Experimental Group

Group in an experiment that is exposed to the independent variable.

Control Group

Group in an experiment that is not exposed to the independent variable used for comparison.

Random Assignment

Process of assigning participants to different groups randomly to reduce bias and ensure equivalence.

Causal Inference

Determining whether a causal relationship exists between the independent and dependent variables.

Internal Validity

The degree to which an experiment accurately establishes a cause-and-effect relationship without interference from confounding variables.

Threats to Internal Validity

Factors that can lead to incorrect conclusions about causal relationships, including history, maturation, testing, instrumentation, and others.

Mortality (Attrition)

The dropout of participants from a study, which can affect the validity of the results.

Diffusion of Treatment

When the control group is inadvertently influenced by information from the experimental group.

Compensatory Rivalry

When the control group changes their behavior in response to knowing they are not receiving treatment.

Demoralization

When participants in the control group feel deprived or discouraged and may alter their behavior as a result.

Construct Validity

The extent to which a test measures the theoretical construct it claims to measure.

External Validity

The generalizability of study findings to other contexts or populations.

Statistical Conclusion Validity

The degree to which conclusions about the relationship between variables are justified based on statistical analysis.

Ethical Considerations in Experiments

Moral issues related to conducting experiments, such as ensuring participants' rights and well-being.

Solomon Four-Group Design

An experimental design that includes two experimental and two control groups, allowing for both pretest and posttest comparisons.

Factorial Design

An experimental design that examines multiple treatments simultaneously to explore interactions between them.

The Classical Experiment

Referred to as the 'gold standard' in research design, it includes independent and dependent variables, pretesting and posttesting, and random assignment.

Study Design

The overall strategy used to integrate the different components of the study in a coherent and logical way, ensuring it effectively addresses the research problem.

Randomized Control Trial (RCT)

An experimental study design that randomly assigns participants into an experimental group or a control group to ensure that any differences in outcomes can be attributed to the intervention.

Blinding

A method used in experiments where participants (single-blind) or both participants and researchers (double-blind) do not know which group participants are in to minimize bias.

Confounding Variable

An external variable that may influence both the independent and dependent variable, potentially leading to erroneous conclusions in the study.

Longitudinal Study

A research design that follows the same subjects over a period of time to observe changes and developments.

Cross-Sectional Study

A study that examines data from a population at a single point in time, allowing for the analysis of various variables simultaneously.

Pilot Study

A small-scale preliminary study conducted to test the feasibility, time, cost, and adverse events involved in a research project before full-scale implementation.

Quasi-Experimental Design

A type of research design that lacks random assignment, but still aims to evaluate the impact of an intervention, often using pre-existing groups.

Population

The entire group of individuals or instances about whom the research question is concerned.

Sample

A subset of the population selected for the study, used to make inferences about the entire population.

Operationalization

The process of defining the measurement of a phenomenon that is not directly measurable, allowing it to be quantified and analyzed.