Ninth Edition CoverGraziano & Raulin
Research Methods (9th edition)

Glossary Items Starting with "N"

naive empiricism
Extreme dependence on one's personal experience in order to accept events as facts. For example, "If I can't see it, then it does not exist."

naturalistic level of constraint
Research carried out in natural settings in which the researcher makes no attempt to manipulate the environment as part of the research.

naturalistic observation
Observing the natural flow of behavior in natural settings.

negative correlation
Relationship between two variables in which an increase in one variable predicts a decrease in the other.

negative practice effects
A decrease in performance on a dependent measure that results from previous exposure of the participant to the measurement procedures.

negatively skewed
When scores are concentrated near the top of the distribution.

Connectionist models are sometimes referred to as neuro-networks because they are designed to resemble the massive interconnections between units that are typical of brain neurons. However, most theorists argue that the connectionist models now in use are dramatic oversimplifications of neural processes and, therefore, one should be cautious in using terms such as neuro-networks to describe them.

A field that studies the relationships of brain functioning to behavior.

neurotransmitter agonists
A chemical substance that enhances the action of a neurotransmitter.

neurotransmitter antagonists
A chemical substance that blocks the action of a neurotransmitter.

no-treatment control group
A control group in a treatment study that receives no treatment of any kind.

nominal data
Data produced when a nominal scale of measurement is used. Nominal data are frequencies of participants in each of the specific categories.

nominal fallacy
The tendency to confuse a label for a behavior as the explanation for the behavior. For example, labeling people as kind because they do many kind things for other people is reasonable, but it is unreasonable to then say that they do those kind things because they are kind people.

nominal scale
Scale of measurement in which only categories are produced as scores. Examples are diagnostic classification, gender of the participant, and political affiliation.

nonequivalent control-group design
Quasi-experimental design in which two or more groups that may not be equivalent at the beginning of the study are compared on the dependent measure.

nonexperimental designs
Any research design that fails to provide adequate controls for confounding.

nonexperimental approaches
See nonexperimental designs.

nonlinear relationship
Any relationship between two or more variables that is characterized by a scatter plot in which the points tend to cluster around a curved instead of a straight line. Most correlations coefficients are insensitive to nonlinear relationships.

nonmanipulated factors
Independent variables in a factorial design in participants are assigned to groups on the basis of some preexisting factor. See differential research.

nonmanipulated independent variable
The preexisting variable that determines group membership in a differential research study.

nonparametric statistics
Inferential statistical procedures that do not rely on estimating such population parameters as the mean and variance.

nonprobability sampling
Any sampling procedure in which some participants have a higher probability of being selected than other participants or the selection of a given participant changes the probability of selecting other participants. Often contrasted with probability sampling.

nonreactive measure
Any dependent measure that provides consistent scores regardless of whether the participant is aware or unaware of being measured.

nonsystematic within-groups variance
Variance due to random factors that affect some participants more than others. Also called error variance.

N-of-one designs
See single-subject experimental designs.

normal distribution
Distribution of scores that is characterized by a bell-shaped curve in which the probability of a score drops off rapidly from the midpoint to the tails of the distribution. A true normal curve is defined by a mathematical equation and is a function of two variables (the mean and variance of the distribution). Normal distributions are useful in psychology because psychological variables tend to show distributions that are close to normal.

null hypothesis
States that the participants from each group are drawn from populations with identical population parameters. The null hypothesis is tested by inferential statistics.