**attrition: **reduction in the number of research participants as some drop out over time

**case study: **exploring a single case or situation in great detail. Information may be gathered with the use of observation, interviews, testing, or other methods to uncover as much as possible about a person or situation

**cohort: **a group of people who are born at roughly the same period in a particular society. Cohorts share histories and contexts for living

**content analysis: **involves looking at media such as old texts, pictures, commercials, lyrics or other materials to explore patterns or themes in culture

**control group: **a comparison group that is equivalent to the experimental group, but is not given the independent variable

**correlation: **the relationship between two or more variables; when two variables are correlated, one variable changes as the other does

**correlation coefficient: **number from -1 to +1, indicating the strength and direction of the relationship between variables, and usually represented by r

**correlational research: **research that formally tests whether a relationship exists between two or more variables, however, correlation does not imply causation

**cross-sectional research: **used to examine behavior in participants of different ages who are tested at the same point in time; may confound age and cohort differences

**dependent variable: **the outcome or variable that is supposedly affected by the independent variable

**descriptive studies: **research focused on describing an occurrence

**double-blind: **a research design in which neither the participants nor the researchers know whether an individual is assigned to the experimental group or the control group

**experimental group: **the group of participants in an experiment who receive the independent variable

**experimental research: **research that involves randomly assigning people to different conditions and using hypothesis testing to make inferences about how these conditions affect behavior; the only method that measures cause and effect between variables

**experiments: **designed to test hypotheses in a controlled setting in efforts to explain how certain factors or events produce outcomes; the only research method that measures cause and effect relationships between variables

**explanatory studies: **research that tries to answer the question “why”

**Hawthorne effect: **individuals tend to change their behavior when they know they are being watched

**hypotheses: **specific statements or predictions about the relationship between variables

**independent variable: **something that is manipulated or introduced by the researcher to the experimental group; treatment or intervention

**longitudinal research: **studying a group of people who may be of the same age and background (cohort), and measuring them repeatedly over a long period of time; may confound age and time of measurement effects

**negative correlation: **two variables change in different directions, with one becoming larger as the other becomes smaller; a negative correlation is not the same thing as no correlation

**observational studies: **also called naturalistic observation, involves watching and recording the actions of participants

**operationalized: **concepts transformed into variables that can be measured in research

**positive correlation: **two variables change in the same direction, both becoming either larger or smaller

**qualitative research: **theoretical ideas are “grounded” in the experiences of the participants, who answer open-ended questions

**quantitative research: **involves numerical data that are quantified using statistics to understand and report what has been studied

**reliability: **when something yields consistent results

**research design: **the strategy or blueprint for deciding how to collect and analyze information; dictates which methods are used and how

**scatterplot: **a plot or mathematical diagram consisting of data points that represent two variables

**secondary content analysis: **archival research, involves analyzing information that has already been collected or examining documents or media to uncover attitudes, practices or preferences

**selective attrition: **certain groups of individuals may tend to drop out more frequently resulting in the remaining participants longer being representative of the whole population

**sequential research design: **combines aspects of cross-sectional and longitudinal designs, but also adding new cohorts at different times of measurement; allows for analyses to consider effects of age, cohort, time of measurement, and socio-historical change

**survey: **asking a standard set of questions to a group of subjects

**validity: **when something yields accurate results

**variables: **factors that change in value