Internal Validity and Research Design Challenges

Observer bias

A threat to internal validity where the researcher's expectations influence their observations.

Demand characteristics

Cues in an experiment that suggest to participants how they should behave.

Placebo

An inactive substance or treatment used as a control in an experiment.

Selection

A threat to internal validity that occurs when participants are not randomly assigned to conditions.

Measurement error

The difference between the actual value and the measured value.

Individual differences

Variations among individuals that can affect study outcomes.

Situation noise

Extraneous variables in the environment that can affect the results of a study.

Floor effects

A situation in which a measure has a lower limit that prevents it from capturing lower scores.

Attrition

A threat to internal validity that occurs when participants drop out of a study.

History

A threat to internal validity that refers to events occurring between the pretest and posttest that may affect results.

Maturation

Changes in participants over time that may affect study outcomes.

Regression

A statistical phenomenon where extreme scores tend to move closer to the mean on subsequent measurements.

Design confound

An alternative explanation for an effect due to a flaw in the study's design.

Selection effect

A threat to internal validity that occurs when groups differ in ways other than the treatment.

Order effect

A threat to internal validity that occurs when the order of conditions affects the results.

Maturation effect

Changes in participants that occur naturally over time, which can affect study results.

Manipulation check

A measure used to determine if the manipulation of the independent variable was successful.

Double-blind study

An experimental design where both participants and researchers are unaware of the conditions.

Placebo effect

A phenomenon where participants experience changes simply because they believe they are receiving treatment.

Weak manipulations

Insufficiently strong interventions that fail to produce a noticeable effect.

Large sample size

A study design feature that can enhance the reliability of results.

Testing

A threat to internal validity that occurs when participants are tested multiple times.

Causal association

A relationship where one variable directly influences another.

Convergent validity

The degree to which two measures of constructs that theoretically should be related, are in fact related.

Criterion validity

The extent to which a measure is related to an outcome.

Face validity

The degree to which a measure appears to measure what it is supposed to measure.

Discriminant validity

The degree to which a measure does not correlate with other measures that it should not correlate with.

Zero association

A situation where there is no relationship between two variables.

Interrater reliability

The degree of agreement among raters or judges.

Test-retest reliability

The consistency of a measure when the same test is administered to the same group at different times.

Cronbach's alpha

A statistic used to measure the internal consistency of a set of items.

Masked study design

Participants unaware of study's true purpose.

Blind study design

Participants and researchers unaware of group assignments.

Behavior traces

Indirect measures of behavior rather than direct observation.

Double-barreled question

Asks two questions in one, causing confusion.

Open-ended questions

Allow detailed responses but require coding for analysis.

Socially desirable responding

Participants answer to appear favorable to others.

Fence-sitting

Choosing neutral response on controversial survey questions.

WEIRD samples

Western, Educated, Industrialized, Rich, and Democratic populations.

Replicable results

Study yields consistent results upon repetition.

Conceptual replication

Same research question, different methods or variables.

Quasi-experiment

Lacks random assignment but compares groups.

File-drawer problem

Publication bias towards significant results over null findings.

Informed consent

Participants must understand study before agreeing.

Debriefing session

Post-study explanation, especially after deception.

Belmont Report

Guidelines for ethical research involving human subjects.

Principle of beneficence

Maximize benefits while minimizing risks to participants.

Principle of justice

Fair distribution of research benefits and burdens.

Principle of respect for persons

Acknowledges autonomy and protects vulnerable populations.

Institutional Review Board (IRB)

Committee ensuring ethical standards in research.

Confidential data

Participant identities linked but protected from disclosure.

Anonymous data

No identifying information collected from participants.

Risk-benefit analysis

Evaluating potential harms against research value.

Incentive ethics

Avoid undue influence through excessive participant rewards.

Semantic differential question

Measures attitudes using bipolar adjectives.

Implicit Association Test

Measures unconscious biases through reaction times.

Regression to the mean

Extreme scores tend to move closer to average.

History threat

External events affecting study outcomes over time.

Maturation threat

Changes in participants affecting study results over time.