AP Psychology Unit 0: Methods and Approaches

Experiment

A research method in which variables are manipulated and controlled to test hypotheses; allows researchers to determine cause-and-effect relationships

Independent Variable

The variable that is manipulated or changed by the researcher in an experiment; the presumed cause

Dependent Variable

The variable that is measured or observed in an experiment; the presumed effect that may change in response to the independent variable

Control Variable

Variables that are kept constant across all conditions to prevent them from affecting the results and confounding the experiment

Population

The entire group of individuals or subjects that a researcher is interested in studying

Representative Sample

A subset of the population that accurately reflects the characteristics and diversity of the larger population

Representativeness

The degree to which a sample accurately reflects the characteristics of the population from which it was drawn

Experimental Group

The group in an experiment that receives the treatment or manipulation of the independent variable

Control Group

The group in an experiment that does not receive the treatment; used as a baseline for comparison

Random Sampling

A method of selecting participants from a population in which every member has an equal chance of being chosen

Randomly Assigned

The process of placing participants into experimental or control groups using random procedures to ensure groups are equivalent

Bias of Selection

Systematic error that occurs when certain members of a population are more likely to be selected than others

Self-Selection Bias

A type of selection bias where participants volunteer to participate

Pre-Screening/Advertising Bias

Bias that occurs when the way a study is advertised or screened attracts certain types of participants

Healthy User Bias

A type of selection bias where healthier or more motivated individuals are more likely to participate in a study

Single-/Double-Blind Design

A research design where participants (single-blind) and/or researchers (double-blind) are unaware of which group receives the treatment

Placebo

An inert substance or fake treatment given to the control group that has no actual effect but may produce psychological or physiological responses

Correlational Research

A research method that examines the relationship between two variables without manipulating either; cannot determine causation

Confounding/Third/Extraneous Variable

A variable other than the independent variable that could affect the dependent variable and alternative explanations for results

Surveys

A research method using questionnaires or interviews to gather information about attitudes

Longitudinal Studies

A research design that follows the same participants over an extended period of time to observe changes

Cross-Sectional Studies

A research design that compares different groups or age cohorts at a single point in time

Clinical Research

Research conducted on individuals with specific disorders or conditions

Case Studies

An in-depth investigation of a single individual

Generalizable

The extent to which research findings can be applied to broader populations or situations beyond the study sample

Conceptual Definition

A definition that explains the meaning of a concept in theoretical terms; describes what something is in general

Operational Definition

A definition that specifies how a variable will be measured or manipulated in a specific study; describes how to measure something

Internal Validity

The extent to which a study accurately measures the effect of the independent variable on the dependent variable; confidence in cause-and-effect conclusions

External Validity

The extent to which research findings can be generalized to other populations

Reliability

The consistency and repeatability of measurements; a test produces similar results when administered multiple times

Inter-Rater Reliability

The degree of agreement between two or more independent observers or raters evaluating the same phenomenon

Naturalistic Observation

A research method in which participants are observed in their natural environment without manipulation or control

Qualitative Research

A research approach focused on understanding experiences and meanings through non-numerical data like interviews and observations

Descriptive Statistics

Statistical methods used to summarize and describe the characteristics of data; includes measures of central tendency and variability

Inferential Statistics

Statistical methods used to test hypotheses and make inferences about populations based on sample data

Central Tendency

A statistical measure that describes the center or typical value of a distribution; includes mean

Mean

The average of all scores in a distribution; calculated by summing all values and dividing by the number of values

Mode

The most frequently occurring score or value in a distribution

Bimodal

A distribution with two modes; two values appear with equal highest frequency

Median

The middle score in a distribution when values are arranged in order; the 50th percentile

Normal Curve

A bell-shaped symmetrical distribution where most scores cluster around the mean and frequencies taper off at the extremes

Range

The difference between the highest and lowest scores in a distribution; a simple measure of variability

Variability

The spread or dispersion of scores around the mean in a distribution; how much scores differ from each other

Standard Deviation

A measure of variability that indicates the average distance of scores from the mean; most commonly used measure of spread

Percentile

A score indicating the percentage of the distribution that falls below that score; used to rank and compare individual scores

Positive Skew

An asymmetrical distribution with a tail extending toward higher values; mean is greater than the median

Negative Skew

An asymmetrical distribution with a tail extending toward lower values; mean is less than the median

Correlation Coefficient

A numerical measure of the strength and direction of a relationship between two variables; ranges from -1 to +1

Pearson Correlation Coefficient

A statistical measure of the linear relationship between two continuous variables; most commonly used correlation coefficient

Positive Correlation

A relationship where two variables move in the same direction; as one increases

Negative Correlation

A relationship where two variables move in opposite directions; as one increases

Sample Size

The number of participants or observations included in a study; larger samples generally provide more reliable results

Null Hypothesis

A statistical hypothesis that states there is no significant relationship or difference between variables

Alternative Hypothesis

A statistical hypothesis that states there is a significant relationship or difference between variables; what researchers expect to find

Alpha

The significance level set before conducting a statistical test; typically set at .05; the probability of committing a Type 1 error

Type 1 Error

A false positive error occurring when researchers reject the null hypothesis when it is actually true; concluding an effect exists when it does not

Type 2 Error

A false negative error occurring when researchers fail to reject the null hypothesis when it is actually false; missing an effect that exists

P-Value

The probability of obtaining results as extreme or more extreme than the observed results if the null hypothesis is true; used to determine statistical significance

Deception

A research method in which participants are misled about the true purpose of a study; raises ethical concerns

Stanley Milgram

A psychologist famous for his obedience studies using deception with confederates; raised questions about ethics in research

Confederates

Research assistants who pose as participants or bystanders to manipulate social situations and observe real participants' behavior

Institutional Review Boards (IRBs)

Committees that review and approve research proposals to ensure they meet ethical standards and protect participant rights

Informed Consent

The ethical principle that participants must be informed about the study's procedures and risks and voluntarily agree to participate

Debriefing

The process of informing participants about the true purpose of the study and addressing any misconceptions or distress after participation

Confidentiality

The ethical principle that researchers must keep participants' identities and personal information private and protected