Contents

Glossary 451than that ordinarily encountered in daily life or during the performance of routinetests.mode The score that appears most frequently in the distribution.multimethod approach Approach to hypothesis testing that seeks evidence by collectingdata using several different research procedures and measures of behavior; arecognition of the fact that any single observation of behavior is susceptible to errorin the measuring process.multiple-baseline design (across individuals, across behaviors, across situations) Asingle-subject experimental design in which the effect of a treatment is demonstratedby showing that behaviors in more than one baseline change as a consequence of theintroduction of a treatment; multiple baselines are established for different individuals,for different behaviors in the same individual, or for the same individual in differentsituations.N 1 designs See single-subject experiment.narrative record Record intended to provide a more or less faithful reproduction ofbehavior as it originally occurred.natural groups design Type of independent groups design in which the conditionsrepresent the selected levels of a naturally occurring independent variable, for example,the individual differences variable age.naturalistic observation Observation of behavior in a more or less natural settingwithout any attempt by the observer to intervene.negative correlation A relationship between two variables in which values for onemeasure increase as the values of the other measure decrease.nomothetic approach Approach to research that seeks to establish broad generalizationsor laws that apply to large groups (populations) of individuals; the average ortypical performance of a group is emphasized.nonequivalent control group design Quasi- experimental procedure in which a comparisonis made between control and treatment groups that have been established onsome basis other than through random assignment of participants to groups.nonprobability sampling A sampling procedure in which there is no way to estimatethe probability of each element’s being included in the sample; a common type isconvenience sampling.novelty effects Threats to internal validity of a study that occur when people’sbehavior changes simply because an innovation (e.g., a treatment) produces excitement,energy, and enthusiasm; a Hawthorne effect is a special case of noveltyeffects.null hypothesis (H 0 ) Assumption used as the first step in statistical inference wherebythe independent variable is said to have had no effect.null hypothesis significance testing (NHST) A procedure for statistical inferenceused to decide whether a variable has produced an effect in a study. NHST beginswith the assumption that the variable has no effect (see null hypothesis), and probabilitytheory is used to determine the probability that the effect (e.g., a mean differencebetween conditions) observed in a study would occur simply by error variation(“chance”). If the likelihood of the observed effect is small (see level of significance),assuming the null hypothesis is true, we infer the variable produced a reliable effect(see statistically significant).observer bias Systematic errors in observation often resulting from the observer’s expectanciesregarding the outcome of a study (i.e., expectancy effects).omnibus F-test The initial overall analysis based on ANOVA.operational definition Procedure whereby a concept is defined solely in terms of theobservable procedures used to produce and measure it.