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Hypothesis Testing

A formal procedure to decide if sample results support a theory about a population.

Null Hypothesis (H0)

Assumes no effect or difference; serves as a default position.

Alternative Hypothesis (H1)

Represents what the researcher aims to prove, stating there is an effect or a difference.

Statistical Significance

A result is significant if it is unlikely to have occurred under the null hypothesis, often denoted as p < 0.05.

Distribution of Sample Means

The theoretical distribution of the means of all possible samples derived from a population.

Critical Value

A threshold in hypothesis testing beyond which the null hypothesis is rejected.

Type I Error

Rejecting the null hypothesis when it is actually true; a false positive.

Type II Error

Failing to reject the null hypothesis when it is false; a false negative.

Power of a Test

The probability of correctly rejecting the null hypothesis when it is false; the ability to detect an effect.

Degrees of Freedom (df)

The number of values in a calculation that are free to vary; used in calculating the t distribution.

T-Test

A statistical test used to compare the means of two groups when the population variance is unknown.

Single Sample T-Test

Compares the mean of a single sample to a known population mean.

Dependent Means T-Test

Compares means from the same participants under two different conditions.

Independent Groups T-Test

Compares means of two different groups of participants.

Cohen's d

A measure of effect size that indicates the standardized difference between two means.

Confidence Interval (CI)

A range of values that is believed to encompass the true population parameter with a certain level of confidence.

Z-Score

A statistical measurement that describes a value's relation to the mean of a group of values; expressed in standard deviations.

Normal Distribution

A bell-shaped distribution where most of the data points cluster around the mean, with symmetry on either side.

Pearson’s r

A correlation coefficient that measures the strength and direction of the linear relationship between two variables.

Scatterplot

A visual representation of the relationship between two quantitative variables.

Sampling Variability

The variation in sample statistics from different samples drawn from the same population.

Sampling Error

The difference between a sample statistic and the actual population parameter.

Longitudinal Study

A research design that involves repeated observations of the same variables over long periods of time.

Quasi-Experimental Design

An empirical study observing subjects in the real world without random assignment to conditions.

Confounding Variables

Extraneous variables that are not accounted for which can affect the dependent variable in a study.

Operational Definition

A statement of the procedures or ways in which a researcher is going to measure a variable.

Circular Reasoning

A logical fallacy where the reasoner begins with what they are trying to end with; the conclusion is included in the premise.

Skewness

A measure of the asymmetry of the probability distribution of a real-valued random variable.

Kurtosis

A descriptor of the shape of a probability distribution that indicates the presence of outliers.

Empirical Rule

A statistical rule that states for a normal distribution, about 68% of the data falls within one standard deviation of the mean.

Random Sampling

A sampling technique where each member of the population has an equal chance of being selected.

Haphazard Sampling

A sampling technique where samples are taken at random but not in a way that ensures equal selection chances.

Probability Value (p-value)

A measure that helps to determine the statistical significance of results.

Statistical Test

A method for making statistical inferences about populations based on sample data.

Central Limit Theorem

States that the sampling distribution of the sample mean will approach a normal distribution as the sample size increases.

Hypothetico-Deductive Method

A scientific method for testing hypotheses through observation and experimentation.

Random Assignment

The process of assigning participants to different groups using randomization to ensure equal chance.

Informed Consent

A process in which participants are fully informed about the research and voluntarily agree to participate.

Deception in Research

A practice in some psychological research wherein participants are misled about the true purpose of the study.

Debriefing

The process after an experiment where participants are informed about the study's purpose and methods used.

Plagiarism

The practice of taking someone else's work or ideas and passing them off as one's own.

Replication in Research

Repetition of a study's methodology to determine whether the original findings can be consistently reproduced.

Field Study

An observational study that takes place in a natural setting rather than a laboratory.

Cross-Sectional Study

Analyses data from a population at a specific point in time.

Case Study Method

A research method that involves the detailed study of a phenomenon in its real-life context.

Pseudoscience

A collection of beliefs or practices mistakenly regarded as being based on the scientific method.

Findings

Results or conclusions drawn from research or analysis.

Longitudinal Study

A research design that involves repeated observations of the same variables over long periods of time.

Survey Research

Collection of data by having people answer a series of questions.

Observational Research

A study in which a researcher observes and records behavior without manipulating variables.

Systematic Observation

A method of observing behavior that involves careful, structured, and replicable procedures.

Variables

Any characteristic, number, or quantity that can be measured or counted.

Extraneous Variables

Variables that are not of primary interest but could influence the dependent variable.

Causation

The action of causing something; the relationship between cause and effect.

Predictive Validity

The extent to which a score on a scale or test predicts scores on some criterion measure.

Construct Validity

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

Content Validity

The extent to which a measure represents all facets of a given construct.

Face Validity

The extent to which a test appears to measure what it is supposed to measure.

Statistical Power

The likelihood of finding a statistically significant result when there is a true effect.

Research Design

The framework for collecting and analyzing data.

Meta-Analysis

A statistical analysis that combines the results of multiple scientific studies.

Bias in Sampling

A systematic error that results in an unrepresentative sampling.

Operationalization

The process of strictly defining variables into measurable factors.

Naturalistic Observation

A research method involving observing subjects in their natural environment.

Behavioral Measures

Quantifiable, observable behaviors that can be recorded.

Physiological Measures

Biological responses indicating a participant’s state.

Inter-rater Reliability

A measure of agreement among observers on how they record and classify a set of data.

Test-Retest Reliability

A measure of the consistency of a psychological test or assessment.

Internal Validity

The degree to which an experiment accurately establishes a cause-and-effect relationship.

External Validity

The extent to which results of a study can be generalized to, or have relevance for, settings, people, times, and measures other than the ones used in the study.

Statistical Analysis

The process of collecting and interpreting data in order to identify trends and take decisions.

Error Variance

The degree of variability in data that cannot be attributed to the independent variable.

Sampling Bias

A bias in which some members of a population are less likely to be included than others.

Observational Bias

Systematic errors that occur when observations are affected by the observer’s expectations.

Interaction Effects

The way different factors may affect each other in a study or experiment, leading to results that differ from main effects.

Latent Variable

A variable that is not directly observed but is inferred from other variables.

Causal Inference

The act of drawing conclusions about a causal connection based on evidence and reasoning.

Random Error

The chance variation in a measurement due to unpredictable factors.