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Experimental Psych Exam 2

Terms in this set (28)

factorial design
an experimental design in which every level of one independent variable is combined with every level of every other independent variable.
main effect
the independent effect of one independent variable in a factorial design on the dependent variable. There are as many of these as there are independent variables.
interaction
when the effect of one independent variable on the dependent variable in a factorial design changes over the levels of another independent variable.
simple main effect
in a factorial analysis of variance (ANOVA), the effect of one factor at a given level (or combination of levels) of another factor (or factors).
mixed design
an experimental design that includes between-subjects as well as within-subjects factors. Also called a split-plot design.
nested design
an experimental design with a within-subjects factor in which different levels of one independent variable are included under each level of a between-subjects factor.
covariate
a correlational variable (usually a characteristic of the subject) included in an experiment to help reduce the error variance in statistical tests.
quasi-independent variable
a variable resembling an independent variable in an experiment, but whose levels are not assigned to subjects at random.
analysis of covariance (ANOCOVA)
variant of the analysis of variance used to analyze data from experiments that include a correlational variable.
power
the ability of an experimental design or inferential statistic to detect an effect of a variable when an effect is present.
effect size
the amount by which a given experimental manipulation changes the value of the dependent variable in the population, expressed in standard deviation units.
data transformation
mathematical operation applied to raw data, such as taking the square root or arcsine of the original scores in a distribution. Often applied to data that violate the assumptions of parametric statistical tests to help them meet those assumptions.
linear transformations
transformations that simply change the magnitude of the numbers representing your data, but they do not change the scale of measurement. (e.g., adding, subtracting, multiplying, dividing).
carryover effect
a problem associated with within-subjects designs in which exposure to one level of the independent variable alters the behavior observed under subsequent levels.
learning
if the subject learns how to perform a task in the first treatment, performance is likely to be better if the same or similar tasks are used in subsequent treatments.
fatigue
if performance in earlier treatments leads to this, then performance in later treatments may deteriorate, regardless of any effect of the independent variable.
habituation
under some conditions, repeated exposure to a stimulus leads to reduced responsiveness to that stimulus because the stimulus is becoming mroe familiar or expected.
sensitization
sometimes exposure to one stimulus can cause subjects to response more strongly to another stimulus.
potential startle
a rat will show an exaggerated startle response to a sudden noise if the rat has recently received a brief foot shock in the same situation.
adaptation
if subjects go through a period of this, then earlier results may differ from later results because of the adaptive changes.
tolerance
adaptation to the drug which causes a reduced response.
counterbalancing
a technique used to combat carryover effects in within-subjects designs. this involves assigning the various treatments of an experiment in a different order for different subjects.
complete counterbalancing
a type of counterbalancing that provides every possible orderng of treatments and assigns at least one subject to each ordering.
partial counterbalancing
a type of counterbalancing that includes only some of the possible treatment orders; the orders to be retained are chosen randomly from the total set with the restriction that each treatment appear equally often in each position.
differential carryover effects
when the magnitude of the carryover effect differs for different orders of treatment presentation, counterbalancing may be ineffective.
irreversible change
the most serious asymmetry in carryover effects; the classic type of this that produced by a treatment such as brain lesioning-the effects of the operation, once present, cannot be undone.
single-factor two-level design
simplest form of within-subjects design and includes just two levels of a single independent variable; all subjects receive both levels of the variable, but half the subjects receive the treatments in one order andhalf in the opposite order.
single-factor multilevel design
a single group of subjects is exposed to three or more levels of a single independent variable; if the indenpendent variable is not a cumulative factor, the the order of treatments is counterbalanced to prevent any carryover effects from confounding the effects of the treatments.
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