Glossary Items Starting with "I"

icon: Small pictures on a computer screen that represent a program, action, or data set. Clicking on the icon will usually start a program or action.
idea-generating phase of research: First step in any research project during which the researcher selects a topic to study.
identity: A characteristic of the abstract number system in which each number has a specific meaning or identity.
incidental comparison: See post hoc test.
incidental learning: Learning that occurs without specific reinforcement, usually while learning a different task.
incomplete counterbalancing: See counterbalancing.
independent-groups design: See between-subjects design.
independent samples: Samples that include different participants in each group and in which the selection of participants for one sample does not influence the selection of participants for any other sample.
independent variable: Any variable in research that defines separate groups of participants. Participants may be assigned to these groups on the basis of either (1) some preexisting characteristics (differential research) or (2) some form of random assignment (experimental research).
individual differences: Natural differences between people. Individual differences tend to obscure effects of an independent variable on the dependent measure(s).
inductive reasoning: Reasoning from the particular to the general. Used to generate theories or models based on particular observations or ideas.
inductive theory: Inductive theories are built on a strong empirical base and tend not to stray far from that empirical base. Often contrasted with deductive theory and functional theory.
inference: Any conclusion drawn on the basis of some set of information. We draw inferences on the basis of empirical data we collect and ideas we construct.
inferential statistics: Statistical procedures that compute the probability of obtaining the particular pattern of data if all participants were actually drawn from the same population. If the probability of obtaining such a pattern of scores is low, we reject the hypothesis that all participants were drawn from the same population (null hypothesis) and conclude that there were meaningful differences between groups or conditions.
informed consent: Critical principle in the ethical treatment of participants. Participants have the right to know exactly what they are getting into and to refuse to participate.
informed consent form: A form that is signed by each human participant prior to the beginning of the study. The informed consent form must present enough detail about the study and its risks to permit participants to make informed decisions about their participation. The consent form should be reviewed and approved by the Institutional Review Board as part of their evaluation of the research proposal.
initial equivalence (principle of): The groups to be compared in an experiment must be equivalent at the start of an experiment.
Institutional Review Board (IRB): Formal body that operates in most institutions that conduct research. The IRB reviews all research proposals to determine if they meet ethical guidelines.
instrumentation: Potential confounding variable involving any change in the measuring instrument over time that causes the instrument to give different readings when no change has occurred in the participant.
instruments subsection: See apparatus section.
interaction effects: Combined effect of two or more independent variables on the dependent variable that is more than the sum of the individual effects. Interactions can be measured only in factorial designs.
internal consistency reliability: Index of how homogeneous the items of a measure. Items that are homogeneous correlate strongly with one another, suggesting that all items are measuring the same characteristic.
internal validity: Accuracy of the research study in determining the relationship between the independent and the dependent variables. Internal validity can be assured only if all confounding variables have been controlled.
interpretation phase of research: Research phase in which the results of statistical analyses of data are interpreted in light of (1) the adequacy of control procedures, (2) previous research, and (3) existing theories about the behavior under study.
interrater reliability: Index of the consistency of ratings between separate raters. It is indexed by the correlation between the ratings of two raters.
interrater reliability coefficient: A correlation coefficient expressing the degree of agreement between two or more raters. See reliability.
interrupted time-series design: Type of research design suitable for either single participants or groups in which multiple measures of the dependent variable are taken before and after an experimental manipulation. Time-series designs provide some control for history and maturation, even without the inclusion of a control group.
interval scale: Scale of measurement in which the distance between any two adjacent scores is the same as the distance between any other two adjacent scores but zero is not a true zero. An example of an interval scale is temperature measured in either Centigrade or Fahrenheit.
interview schedule: A standardized interview, with each question spelled out for the interviewer. Interview schedules provide consistency in interviews.
introduction: The first substantive section of a research paper in which the authors review previous research and theory to provide the framework and rationale for the study.
intuition: A way of acquiring knowledge. In intuition, ideas come to people supposedly without intellectual effort or sensory processes.
invasion of privacy: Ethical issue in research. Researchers should make every effort to protect participants' privacy by maintaining confidentiality of records.