Research Methods & Measurement in Psychology: Variables, Reliability, Validity, and Data Collection

Ways to Measure Variables

Methods researchers use to measure variables, including self-report, observational, and physiological measures.

Operationalization

The specific way a researcher measures or manipulates a variable in a study.

Conceptual Variable

The theoretical idea or construct a researcher wants to study (e.g., anxiety, intelligence).

Operational Definition

The specific procedure used to measure or manipulate a conceptual variable.

Self-Report Measure

A method in which participants answer questions about their own thoughts, feelings, or behaviors.

Self-Report Pros

Easy to administer, inexpensive, and allows researchers to measure internal states like thoughts and emotions.

Self-Report Cons

Participants may lie, misremember, misunderstand questions, or respond with social desirability bias.

Observational Measure

A method where researchers watch and record participants' behaviors.

Observational Pros

Captures real behavior and can be more objective than self-report.

Observational Cons

Time consuming and behavior may change if people know they are being observed.

Physiological Measure

A method that records biological data such as heart rate, hormone levels, or brain activity.

Physiological Measure Pros

Objective and difficult for participants to fake.

Physiological Measure Cons

Expensive and biological signals may not perfectly represent psychological constructs.

Categorical Variable

A variable that places individuals into categories or groups without numerical meaning.

Quantitative Variable

A variable measured with numbers representing amount or degree.

Interval Scale

A quantitative scale with equal intervals between values but no true zero point.

Ratio Scale

A quantitative scale with equal intervals and a true zero point.

Reliability

The consistency or stability of a measurement.

Test-Retest Reliability

The consistency of results when the same test is given to the same people at different times.

Interrater Reliability

The degree to which different observers give consistent estimates of the same behavior.

Internal Reliability

The consistency among multiple items that measure the same construct.

Validity

The extent to which a measure accurately measures what it claims to measure.

Reliability vs Validity

Reliability refers to consistency, while validity refers to accuracy of a measure.

Scatterplot

A graph that displays individual data points showing the relationship between two quantitative variables.

Correlation Coefficient (r)

A statistic that describes the strength and direction of a relationship between two variables.

Positive Correlation

A relationship where both variables increase together.

Negative Correlation

A relationship where one variable increases while the other decreases.

No Correlation

A relationship where changes in one variable are not related to changes in another.

Face Validity

The extent to which a measure appears to measure what it claims to measure.

Content Validity

The extent to which a measure covers all parts of the construct it aims to measure.

Criterion Validity

The extent to which a measure correlates with a real-world outcome or behavior.

Convergent Validity

When a measure correlates strongly with other measures of the same construct.

Discriminant Validity

When a measure does not correlate strongly with measures of different constructs.

Construct Validity of Surveys

The degree to which survey questions accurately measure the intended construct.

Open-Ended Questions

Survey questions that allow participants to answer in their own words.

Force-Choice Questions

Survey questions where participants must select from predetermined answer options.

Question Wording

The specific phrasing of survey questions, which can influence how participants interpret and answer them.

Double-Barreled Question

A question that asks about two different issues at once.

Accuracy of Response

The degree to which participants provide truthful and accurate answers.

Mental Shortcuts (Heuristics)

Simplified strategies participants use when answering questions instead of carefully recalling information.

Self-Reporting "More Than One Can Know"

When participants are asked to explain behaviors or attitudes they may not fully understand.

Memory Errors

Mistakes that occur when participants try to recall past events or experiences.

Construct Validity of Behavioral Observations

The degree to which observed behaviors accurately represent the intended construct.

Observations vs Self-Reports

Observations often have higher construct validity because they measure actual behavior instead of reported behavior.

Reactivity

When participants change their behavior because they know they are being observed.

Solution to Reactivity: Blend In

Researchers reduce their visibility to avoid influencing participants' behavior.

Solution to Reactivity: Wait It Out

Researchers wait until participants become accustomed to being observed.

Solution to Reactivity: Unobtrusive Measures

Researchers use hidden or indirect observation methods.

Generalizability

The extent to which results from a sample apply to a larger population.

Population

The entire group of individuals a researcher wants to study.

Sample

A smaller group selected from the population to participate in a study.

External Validity

The degree to which study results can be generalized to other people or settings.

Unbiased Sample

A sample where every member of the population has an equal chance of being selected.

Probability Sampling

Sampling methods in which the probability of selection for each participant is known.

Random Sampling

Selecting participants completely by chance from the population.

Representative Sample

A sample that accurately reflects the characteristics of the population.

Biased Sample

A sample that does not accurately represent the population.

Convenience Sampling

Selecting participants who are easy to access.

Self-Selection Sampling

A sampling method where participants volunteer to participate.

Random Assignment

Randomly placing participants into experimental groups.

Convenience Sampling (when external validity is not priority)

Using easily available participants to conduct research.

Purposive Sampling

Selecting participants who have specific characteristics relevant to the research question.

Snowball Sampling

Participants recruit additional participants from their social networks.

Quota Sampling

Researchers ensure that certain population subgroups are included in specific numbers.

Frequency Claim

A statement about how often something occurs within a population.

Priority of Frequency Claims

External validity and generalizability are most important.

Sampling Technique vs Sample Size

Sampling method is more important than sample size for generalizability.

Bivariate Correlation

A statistical analysis examining the relationship between two measured variables.

Measured Variables

Variables that are observed and recorded but not manipulated.

Association Claim

A statement suggesting that two variables are related.

Bar Graph

A graph used to display means of groups when there is a categorical variable.

Scatterplot in Correlation

A graph showing individual data points and the relationship between two quantitative variables.

Construct Validity in Association Claims

Evaluating how well the variables are measured.

Statistical Validity

The extent to which statistical conclusions about relationships between variables are accurate.

Effect Size

A statistic that indicates the strength of a relationship between variables.

Outlier

An extreme data point that differs greatly from other observations.

Curvilinear Association

A relationship between variables that changes direction.

Internal Validity

The degree to which a study can establish a causal relationship between variables.

Covariance

Two variables change together.

Temporal Precedence

The cause occurs before the effect.

Third Variable Problem

A situation where an unmeasured variable explains the relationship between two variables.

Correlation Does Not Equal Causation

A relationship between variables does not necessarily mean one causes the other.

External Validity in Correlational Research

The ability to generalize correlational findings to the larger population.

Moderator

A variable that changes the strength or direction of the relationship between two other variables.

Moderators in Research

Moderators help researchers understand when or for whom a relationship occurs.