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| short for ANalysis Of VAriance, the most common inferential statistical tool for analyzing the results of experiments when dependent variables are measured on interval or ratio scales |
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| a standardized method for displaying the results of an ANOVA; includes sources of variance, sums of squares, degrees of freedom, mean squares (variance), F ratios, and probability values |
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| Aptitude by Treatment Interaction design; form of a P x E factorial design found in educational research, the goal of which is to examine possible interactions between an aptitude variable (person factor) and a treatment variable (environmental factor) |
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| name often given to a form of participant bias in which behavior is influenced by the mere knowledge that the participant is in an experiment and is therefor of some importance to the experimenter |
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| form of partial counterbalancing in which each condition of the study occurs equally often in each sequential position and each condition precedes and follows each other condition exactly one time |
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| a factorial design with at least one subject factor (P = person variable) and one manipulated factor (E = environmental variable) |
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| a threat to the internal validity of a study; occurs when participants fail to complete a study, usually but not necessarily in longitudinal studies; those finishing the study may not be equivalent to those who started it |
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| any experimental design in which different groups of participants serve in the different conditions of the study |
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| a procedure used to accomplish random assignment and ensure an equal number of participants in each condition; ensures that each condition of the study has a subject randomly assigned to it before any condition has a subject assigned to it again; also used in within-subjects design as a counterbalancing procedure to ensure that when participants are tested in each condition more than once, they experience each condition once before experiencing any condition again |
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| form of sequence effect in which systematic changes in performance occur as a result of completing one sequence of conditions rather than a different sequence |
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| occurs when scores on two or more conditions are at or near the maximum possible for the scale being used, giving the impression that no differences exist between the conditions |
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| a cohort is a group of people born at about the same time; cohort effects can reduce the internal validity of cross-sectional studies because differences between groups could result from the effects of growing up in different historical eras |
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| in developmental psychology research, a design that combines cross-sectional and longitudinal designs; a new cohort is added to a study every few years, and then studied periodically throughout the time course of the study |
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| complete counterbalancing |
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| occurs when all possible orders of conditions are used in a within-subjects design |
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| any extraneous variable that covaries with the independent variable and could provide an alternative explanation of the results |
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| in measurement, it occurs when the measure being used accurately assesses some hypothetical construct; also refers to whether the construct itself is valid; in research refers to whether the operational definitions used for independent and dependent variables are valid |
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| variable for which an infinite number of values potentially exists (e.g. a drug's dosage level) |
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| a group not given a treatment that is being evaluated in a study; provides a means of comparison |
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| for a within-subjects variable, any procedure designed to control for sequence effects |
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| in developmental psychology, a design in which age is the independent variable and different groups of people are tested; each group is of a different age |
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| any feature of the experimental design or procedure that increases the chances that participants will detect the true purpose of the study |
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| behavior measured as the outcome of an experiment |
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| variable in which each level represents a distinct category that is qualitatively different from another category (e.g., males and females) |
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| a control procedure designed to reduce bias; neither the participant nor the person conducting the experimental session knows which condition of the study is being tested; often used in studies evaluating drug effects |
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| said to exist when research studied psychological phenomena in everyday situations (e.g., memory for where we put our keys) |
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| groups of participants in a between-subjects design that are essentially equal to each other in all ways except for the different levels of the independent variable |
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| on bar or line graphs, they indicate the amount of variability around a mean; often reflect standard deviations or confidence intervals |
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| a form of anxiety experienced by participants that leads them to behave so as to be evaluated positively by the experimenter |
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| a research procedure in which some factor is varied, all else is held constant, and some result is measured |
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| in a study with an identified control group, the experimental group is given the treatment being tested |
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| occurs when an experimenter's expectations about a study affect its outcome |
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| the extent to which the findings of a study generalize to other populations, other settings, and other times |
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| any uncontrolled factor that is not of interest to the researcher but could affect the results |
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| any experimental design with more than one independent variable |
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| a row and column arrangement that characterizes a factorial design and shows the independent variables, the levels of each independent variable, and the total number of conditions (cells) in the study |
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| an experiment that is conducted outside the laboratory; a narrower term than field research |
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| research that occurs in any location other than a scientific laboratory |
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| occurs when scores on two or more conditions are at or near the minimum possible for the scale being used, giving the impression that no differences exist between the conditions |
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| a form of participant bias in which participants try to guess the experimenter's hypothesis and then behave in such a way as to confirm it |
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| a threat to internal validity of a study; occurs when some historical event that could affect participants happens between the beginning of a study and its end |
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| one of the conditions that should be in effect in order to perform parametric inferential tests such a a t test or ANOVA; refers to the fact that variability among all the conditions of a study ought to be similar |
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| independent groups design |
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| a between-subjects design that uses a manipulated independent variable and has at least two groups of participants; subjects are randomly assigned to the groups |
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| independent variable (IV) |
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| the factor of interest to the researcher; it can be directly manipulated by the experimenter (e.g., creating different levels of anxiety in subjects), or participants can be selected by virtue of their possessing certain attributes (e.g., selecting two groups who differ in the normal levels of anxiousness) |
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| type of independent variable in which participants are given different sets of instructions about how to perform (e.g., given a list of stimuli, various groups might be told to process them in different ways) |
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| a threat to the internal validity of a study; occurs when the measuring instrument changes from pretest to posttest (e.g., because of their experience with the instrument, experimenters might use it differently from pretest to posttest) |
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| in a factorial design, occurs when the effect of one independent variable depends on the level of another independent variable |
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| the extent to which a study is free from methodological flaws, especially confounding factors |
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| in developmental psychology, a design in which age is the independent variable and the same group of people are tested repeatedly at different ages |
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| refers to whether or not statistically significant differences exist between levels of the independent variable in a factorial design |
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| in debriefing, a procedure to determine if subjects were aware of a deception experiment's true purpose; also refers to any procedure that determines if systematic manipulations have the intended effect on participants |
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| a between-subjects design that uses a manipulated independent variable and has at least two groups of participants; subjects are matched on some variable assumed to affect the outcome before being randomly assigned to the groups |
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| a procedure for creating equivalent groups in which participants are measured on some factor (a "matching variable") expected to correlate with the dependent variable; groups are then formed by taking participants who score at the same level on matching variable and randomly assigning them to groups |
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| any variable selected for matching participants in a matched groups study |
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| a threat to the internal validity of a study; occurs when participants change from the beginning to the end of the study simply as a result of maturational changes within them and not as a result of some independent variable |
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| a mixed design with at least one subject factor and one manipulated factor |
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| a factorial design with at least one between-subjects factor and one within-subjects factor |
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| nonequivalent groups design |
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| a between-subjects design with at least two groups of participants that uses a subject variable or that creates groups that are nonequivalent |
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| any outcome that does not form a straight line when graphed; can only occur when the independent variable has more than two levels |
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| occurs when a subset of all possible orders of conditions is used in a within-subjects design (e.g., a random sample of the population of all possible orders could be selected) |
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| can occur when the behavior of participants is influenced by their beliefs about how they are supposed to behave in a study |
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| control group in which some participants believe they are receiving the experimental treatment, but they are not |
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| a measurement given to participants at the conclusion of a study after they have experienced a treatment or been in a control group; comparisons are made with pretest scores to determine if change occurred |
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| a measurement given to participants at the outset of a study, prior to their begin given a treatment (or not treated, when participants are in a control group) |
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| in a within-subjects design, any sequence effect in which the accumulated effects are assumed to be the same from trial to trial (e.g., fatigue) |
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| a detailed description of the sequence of events in a research session; used by an experimenter to ensure uniformity of treatment of research participants |
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| one of experimental psychology's original areas of research; investigates the relationship between physical stimuli and the perception of those stimuli; studies thresholds |
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| the most common procedure for creating equivalent groups in a between-subjects design; each individual volunteering for the study has an equal probability of being assigned to any one of the groups in the study |
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| if a score on a test is extremely high or extremely low, a second score taken will be closer to the mean score; can be a threat to the internal validity or a study if a pretest score is extreme and the posttest score changes in the direction of the mean |
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| another name for a within-subject design; participants are tested in each of the experiment's conditions |
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| occurs in a within-subjects design when participants are tested more than once per condition; each experience on sequence, and then a second with the order reversed from the first (e.g., A-B-C-C-B-A) |
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| can occur in a within-subjects design when the experience of participating in one of the conditions of the study influences performance in subsequent conditions |
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| following an ANOVA, a follow-up test to a significant interaction, comparing individual cells |
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| single-factor multilevel design |
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| any design with a single independent variable and more than two levels of the independent variable |
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| type of independent variable in which subjects encounter different environmental circumstances (e.g., large vs. small rooms in a crowding study) |
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| statistical conclusion validity |
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| said to exist when the researcher uses statistical analysis properly and draws the appropriate conclusions from the analysis |
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| group of students asked to participate in research, typically as part of an introductory psychology course requirement; sometimes called a "participant pool" |
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| a threat to the internal validity of a study; occurs when those participating in a study cannot be assigned randomly to groups; hence the groups are nonequivalent |
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| a type of independent variable that is selected rather than manipulated by the experimenter; refers to an already existing attribute of the individuals chosen for the study |
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| t test for independent samples |
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| an inferential statistical analysis used when comparing two samples of data in either an independent groups design or a nonequivalent groups design |
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| t test for related sample |
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| an inferential statistical analysis used when comparing two samples of data in either a matched groups design or a repeated-measures design |
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| type of independent variable in which participant are given different types to tasks to perform (e.g., mazes that differ in level of difficulty) |
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| a threat to the internal validity of a study; occurs when the fact of taking a pretest influences posttest scores, perhaps by sensitizing participants to the purpose of a study |
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| waiting list control group |
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| control group in which participants aren't yet receiving treatment but will, eventually; used ton ensure that those in the experimental and control groups are similar (e.g., all seeking treatment for the same problem) |
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| any experimental design in which the same participants serve in each of the different conditions of the study; also called a "repeated-measures" design |
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| control group in which the treatment given a member of the control group is matched exactly with the treatment given a member of the experimental group |
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