Experimental Psychology
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Complete list of Terms and Definitions for Experimental Psychology

Terms Definitions
psychophysics one of experimental psychology's original areas of research; investigates the relationship between physical stimuli and the perception of those stimuli; studies thresholds
quasi-experiment occurs whenever causal conclusions about the effect of an independent variable cannot be drawn because there is incomplete control over the variables in the study; random assignment not possible in these studies
matching 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
experimenter bias occurs when an experimenter's expectations about a study affect its outcome
partial correlation a multivariate statistical procedure for evaluating the effects of third variables; if the correlation between X and Y remains high, even after some third factor Z has been "partialed out," then Z can be eliminated as a third variable
trends predictable patterns of events that occur over a period of time; evaluated in time series studies
scatterplot a graph depicting the relationship shown by a correlation
multivariate analysis any statistical analysis investigating the relationship between more than two variables
mean average of a set of scores
null hypothesis hypothesis that the differences between two or more population parameters are zero. used nontechnically to refer to the condition that no differences exist between groups in an experiment
confound factor that systmeatically biases the research but was not purposely introduced by the experimenter
hypothesis a statement or expectation developed in relation to an explicit or implicit theory concerning potential outcomes of an experiment
discrete variable variable in which each level represents a distinct category that is qualitatively different from another category (e.g., males and females)
cross-sectional study 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
protocols a detailed description of the sequence of events in a research session; used by an experimenter to ensure uniformity of treatment of research participants
repeated-measures design another name for a within-subject design; participants are tested in each of the experiment's conditions
Latin square 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
posttest 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
progressive effect 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)
event sampling a procedure in observational research in which only certain types of behaviors occurring under precisely defined conditions are sampled
multiple regression a multivariate analysis that includes a criterion variable and two or more predictor variables; the predictors will have different weights
sugging a marketing strategy in which an attempt to sell a prduct is made by disguising the sales pitch with what appears to be a legitimate survey; the term is short for Selling Under the Guise of a survey
behavior checklist lists of behaviors with predefined operational definitions that researchers are trained to use in an observational study
representative sample a sample with characteristics that match those same attributes as they exist in the population
regression analysis in correlational research, knowing the size of a correlation and a value for variable X, it is possible to predict a value for variable Y; this process occurs through a regression analysis
sample some portion or subset of the population
directionality problem in correlational research, this refers to the fact that for a correlation between variables X and Y, it is possible that X is causing Y, but it is also possible that Y is causing X; the correlation alone provides no basis for deciding between the two alternatives
affirming the consequent form of reverse confirmatory reasoning in which one case is used to draw the illogical conclusion relating to all similar cases.If p, then q.p.therefore q.
confounding variables a variable that systematically varies with the independent variable that could provide an alternative explanation for the influence of the independent variable on the dependent variable
deduction reasoning from the general to the particular, as in the case of creating an expected hypothesis for a particular experiment from a general theoretical statement. Opposite of induction.
chance variation occurrence of events without any known antecedent as seen from the standpoint of the experiment
validity accuracy of our ideas and our research; degree to which these are true and capable of support
Thomas Kuhn science goes through series of revolutions, paradigms until another paradigm shift (revolution) takes placestable period between shifts is normal science
standard deviation measure of variability calculated by taking the square root of the variance
operational definiton a definition that presents a construct in terms of observable operations that can be measured and utilized in researchit redefines the concept in terms of clearly observable operations that anyone can see and repeat
y-axis vertical axis of a graph also referred to as the ordinate. dependent variable plotted here
modeling a procedure using either a conceptual or a mathematical model to generate data
quantitative methods methods that emphasize measures using numbers and traditional statistical techniques
random assignment 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
interaction in a factorial design, occurs when the effect of one independent variable depends on the level of another independent variable
evaluation apprehension a form of anxiety experienced by participants that leads them to behave so as to be evaluated positively by the experimenter
task variable type of independent variable in which participant are given different types to tasks to perform (e.g., mazes that differ in level of difficulty)
carryover effect 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
situational variable type of independent variable in which subjects encounter different environmental circumstances (e.g., large vs. small rooms in a crowding study)
block randomization 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
within-subjects design any experimental design in which the same participants serve in each of the different conditions of the study; also called a "repeated-measures" design
history 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
ANOVA source table 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
placebo control group control group in which some participants believe they are receiving the experimental treatment, but they are not
continuous variable variable for which an infinite number of values potentially exists (e.g. a drug's dosage level)
needs analysis form of program evaluation that occurs before a program begins and determines whether the program is needed
quota sample a non-probability sample in which the proportions of some subgroups in the sample are the same as those subgroup proportions in the population
program evaluation a form of applied research that includes a number of research activities designed to evaluate programs from planning to completion
predictor variable in a regression analysis, the variable used to predict the criterion variable (e.g., SAT scores are used to predict college grades)
interview survey a survey method in which the researcher interviews the participant face to face; allows for more in-depth surveying (e.g., follow-up questions and clarification)
convenience sample a non-probability sample in which the researchers requests volunteers from a group of people who meet the general requirements of the study (e.g., teenagers); used in most psychological research, except when specific estimates of population values need to be made
self-selection problem in surveys, when the sample is composed of only those who voluntarily choose to respond, the result can be a biased sample
split-half reliability a form of reliability in which one-half of the items (e.g., the even-numbered items) on a test are correlated with the remaining items
random assignment occurs when a partcipants chances of being assigned to each group in an experiment are equal
consequent the second of two propositions in a logical argument of the form It antecedent is true, then consequent follows.
single-factor multilevel design any design with a single independent variable and more than two levels of the independent variable
yoked control group 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
t test for related sample an inferential statistical analysis used when comparing two samples of data in either a matched groups design or a repeated-measures design
good subject 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
independent groups design 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
simple random sample a probability sample in which each member of the population has an equal chance of being selected as a member of the sample
criterion variable in a regression analysis, this is the variable that is being predicted from the predictor variable (e.g., college grades are predicted from SAT scores)
coefficient of determination (r^2) for two correlated factors, the proportion of variance in one factor that can be attributed to the second factor; found by squaring Pearson's r
Pearson's r measure of the size of a correlation between two variables; ranges from a perfect positive correlation of +1.00 to a perfect negative correlation of -1.00; if r=0, then no relationship exists between the variables
biased sample a sample that is not representative of the population
intraclass correlation a form of correlation used when pairs of scores do not come from the same individual, as when correlations are calculated for pairs of twins
open-ended question a type of question found on surveys that requires a narrative response, rather than a "yes" or "no" answer
inter-observer reliability the degree of agreement between two or more observers of the same event
dependent variable the variable that is measured by the experimenter
random number table table of numbers created so that their occurrence cannot be predicted from a mathematical formula
statistical conclusion validity said to exist when the researcher uses statistical analysis properly and draws the appropriate conclusions from the analysis
homogeneity of variance 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
demographic information any data that can serve to classify or identify individuals (e.g., gender, age, income)
denying the antecedent form of reasoning in which a false premise is illogically concluded to result in a false consequentIf p, then q. Not p. Therfore, not q.
modus ponens (confirmatory reasoning) reasoning that a true premise leads to a true consequentIf p,then q.ptherfore, q.
cohort effects 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
regression to the mean 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