EDUC 500 Midterm Study Guide: Research Designs, Sampling, and Validity

Flashcards covering core educational research methodologies, sampling designs, threats to validity, and experimental frameworks from the EDUC 500 Midterm Study Guide.

Target Population

The entire group of individuals or elements to which a researcher intends to generalize the findings of a study.

Accessible Population (Sampling Frame)

The realistic proportion of the target population that is available and accessible to the researcher from which the sample is drawn.

Sample

A selected subset of individuals chosen from the accessible population to participate in a research investigation.

Representative Sample

A sample whose characteristics closely mirror and accurately represent the essential features of the overall target population.

Simple Random Sampling

A probability sampling technique in which every member of the sampling frame has an equal and independent chance of being selected.

Stratified Random Sampling

A probability sampling method in which the population is divided into distinct subgroups or strata, and individuals are randomly selected from within each stratum.

Systematic Sampling

A probability sampling procedure where individuals are selected from a list according to a predetermined numerical sequence or interval.

Cluster Random Sampling

A probability sampling method where pre-existing, naturally occurring groups or classrooms are randomly selected rather than individual participants, and all individuals within those groups are surveyed.

Convenience Sampling

A non-probability sampling design where participants are chosen based on immediate availability, accessibility, or willingness to volunteer rather than random selection.

Purposive Sampling

A non-probability sampling technique where researchers select participants who satisfy specific, predefined inclusion criteria while excluding those who do not.

Snowball Sampling

A non-probability sampling strategy where existing study participants recruit or refer subsequent participants from their personal or professional networks.

Cross-Sectional Survey Design

A non-experimental survey design that gathers observational or self-report data from a sample at a single, specific point in time.

Longitudinal Survey Design

A survey design in which data are collected from participants or targeted populations over an extended period across multiple time intervals.

Trend Study

A longitudinal survey design that examines changes in a broad population over time by drawing different samples of individuals from that population at each measurement point.

Cohort Study

A longitudinal survey design that tracks a specific subpopulation defined by a shared characteristic or life event over a period of time.

Panel Study

A longitudinal survey design in which the exact same group of individual participants is followed and measured repeatedly over time.

Independent Variable (IV)

The variable manipulated, categorized, or controlled by the experimenter to determine its effect on an outcome; it is structured across distinct levels or conditions.

Dependent Variable (DV)

The measured outcome variable hypothesized to change or differ as a direct consequence of the independent variable.

Extraneous (Confounding) Variable

An uncontrolled variable outside the intended study design that can contaminate the outcome by influencing the dependent variable and confounding the effects of the independent variable.

Internal Validity

The degree to which changes in the dependent variable can be confidently attributed to the manipulation of the independent variable rather than to extraneous factors.

External Validity

The extent to which the findings and causal relationships established in an experiment can be generalized to other populations, settings, times, and contexts.

History Threat

A threat to internal validity involving unanticipated events occurring outside the experiment between pretest and posttest that affect participants' mean performance on the dependent variable.

Maturation Threat

An internal validity threat resulting from biological, developmental, or psychological processes occurring naturally within participants over time that alter the outcome.

Differential Selection

An internal validity threat caused by pre-existing systematic differences between study groups due to the absence of random assignment.

Testing Threat

An internal validity threat where exposure to an initial pretest enhances, sensitizes, or alters participants' subsequent performance on the posttest.

Instrumentation Threat

A threat to internal validity caused by changes in the calibration of testing instruments, scoring standards, or observer bias between repeated measurements.

Statistical Regression Threat

An internal validity threat where participants selected on the basis of extreme initial scores naturally score closer toward the population mean upon retesting.

Attrition (Mortality) Threat

An internal validity threat that occurs when the differential drop-out or loss of participants across groups over time introduces systematic bias into the comparison.

Hawthorne Effect

A reactive arrangement threat to external validity where participants alter or improve their performance simply because they are conscious of being observed and studied.

John Henry Effect

A reactive arrangement threat to external validity where members of an untreated control group perceive a competitive challenge and work harder to outperform the treatment group.

Placebo Effect

A psychological phenomenon where individuals exhibit genuine clinical or behavioral changes because of their expectation of receiving an active intervention.

Solomon Four-Group Design

An experimental design employing four groups (two receiving a pretest and two omitting it) to evaluate and control for pretest-treatment interaction effects.

Factorial Design

An experimental design involving two or more independent variables that allows researchers to study main effects as well as interaction effects among variables.

Random Assignment vs. Random Selection

Random selection determines how individual subjects are drawn from an accessible population into a study sample, whereas random assignment determines how enrolled subjects are allocated to experimental or control conditions.

True Experiment

An experimental design characterized by manipulation of the independent variable, two or more groups, one or more measurement times, and random assignment of individuals to groups, providing the best control of internal validity threats.

Quasi-Experiment

An experimental design featuring manipulation of the independent variable and two or more measurement points, but lacking random assignment of individuals to groups, relying instead on other control methods.

Causal-Comparative Design

A non-experimental research design comparing two or more pre-existing groups on a dependent variable where the independent variable is not manipulated and random assignment is absent.

Pre-Experiment

An experimental design that manipulates an independent variable across one or more groups but lacks random assignment and other control mechanisms, providing the worst control of threats.

Institutional Review Board (IRB)

An administrative committee established to review research proposals involving human participants, ensuring ethical standards, adequate informed consent, data protection, and minimal risk.

Research Design Comparison Matrix

A structured comparative continuum evaluating True Experiment, Quasi Experiment, Causal Comparative, and Pre Experiment across IV manipulation, number of groups, measurement frequency, and threat control methods from best to worst.