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Independent Variables

variable believed to affect or alter status on another variable , viewed as the treatment of intervention


Dependent Variables

status on that variable seems to depend on the status on another variable


Moderator Variables

affects the strength or direction of the relationship between the independent and dependent variable


Mediator Variables

responsible for the observed relationship between variables,


Interval Recording

known as interval sampling and time sampling, and involves observing a behavior for a period of time that has been divided into equal intervals ( 30 minutes that divided into 15 second intervals) and recording whether or not the behavior occurs during each interval, useful for studying complex behaviors that have no clear beginning or end, laughing, talking, playing


Event sampling:

Event recording, entails observing and recording the behavior each time it occurs, recording can take several forms including using a precoded checklist or recording the times when the behavior began and ended, studying behaviors that occur infrequently, have a long duration


True vs Quasi Experimental Research

True Experimental: provides amount of control necessary to conclude that observed variability in a dependent variable is caused by variability in an independent variable, able to randomly assign subjects to different treatment groups
Quasi Experiment: investigating the effects of an independent variable on a dependent variable, but does not provide an investigator with the same degree of experimental control, cannot control assignments of groups


Random assignment vs random selection

random assignment helps ensure that any observed differences between groups on the dependent variable are actually due to the effects of the independent variable and refers to way subjects are assigned to different levels of the IV,
Random selection- way subjects are selected from the population and enables the investigator to generalize his or her findings from the sample to the population


Simple Random Sampling

when using this method, every member of the population has an equal chance of being included in the sample, and selection of one member from the population has no effect on the selection of another member, reduces probability that the sample will be biased in some way


Stratified Random Sampling

when population of interest varies in terms of specific strata that are relevant to the resarch hypothesis, ensure that each stratum is represented in the sample, dividing population into appropriate strata, random selecting subjects from each strata, such as age, gender, education, ses,


Cluster Sampling

using simple or statified sampling to select units or clusters rather than individuals and including all individuals in the selected unit or random selecting indiividuals from each unit


Random Error

experimental research helps an investigator minimize the effects of random fluctations in subjects, conditions, investigator can make sure that subjects do not become fatigued, setting is free of distractions


Random assignment

- can equalize the effects of known and unknown extraneous variables by randomly assigning subjects to different levels of the IV



match subjects in terms of their status on the extraneous variable and then randomly assign to a treatment group, matching is useful when the sample size is too small to guarantee that random assignment will equalize groups



controlled by using it in the study as an additional independent variable so its effects on the dependent variable can be analyzed, grouped on the basis of their status on the extraneous variable and subjects in each block are then randomly assigned to treatment groups


Statistical Control

when an investigator has information on each subjects status or score on an extraneous variable, he or she can use the ANCOVA to remove any variability in the dependent variable that is due to the extraneous variable


Internal Validity

when it allows an investigator to determine if there is a casual relationship between IV and DV, internal validity is threatened when cannot control effects of an extraneous variable, minimize random error, and maximize the effects of the IV



refers to any biological or psychological change that occurs within subjects during the course of the study as a function of time, is not relevant to the research hypothesis, and affects the status on most or all subjects on the dependent variable . fatigue, boredom, hunger



threatens a studys internal validity when an external event affects the status of subjects on the dependent variable, more likely to be a problem when there is only one group, an event occurs at the same time the independent variable is applied


Statistical Regression

threat to a study's internal validity whenever the method used to assign subjects to treatment groups results in systematic differences between the groups at the beginning of the study.



when groups are not equal, selection can act alone or can interact with other factors to threaten a studys internal validity,


External Validity

when its results can be generalized to other people, settings or conditions,, external validity is always limited by its internal validity


Pretest Sensitization

administration of a pretest can sensitize subjecs to the purpose of the research and alter their reaction to the IV. when the results have been contaminated , they cannot be generalized to ppl who have no been pretested,


Solomon Four Square-

- which allows an investigator to measure the impact of pretesting of both external and internal validity, pretest is treated as an additional IV


Reactivity/Demand Characteristics

participants may respond to an IV in a particular way because they know their behavior is being observed, when reactivity happens, results cannot be generalized to conditions where reactivity is not present

Demand Chacteristics: cues in the experimental setting that inform subjects of the purpose of the study or suggest what behaviors are expected of them.


Multiple Treatment Interference/Counterbalancing

Study involves exposing subjects to two or more levels of an IV, the effects of one level of the IV can be affected by previous exposure to another level.
Can be controlled by using a counterbalanced design in which different subjects receive the levels of the IV in a different order
*Latin square design is one type of counterbalanced design and involves administering each level of hte IV so it appears the same number of times in each position


Between groups designs

effects of different levels of an independent variable are assessed by adminstering each level to a different group of subjects and comparing the status or performance of the groups on the DV. *simplest includes two groups that receive a different level of the IV


Within Subjects Design

all levels of theIV are adminstered sequentially to all subjects,
simple group time series design- effects of a a reamtnet are evaulated by measuring the DV several times at regular intervals before and after the treatment is applied


Mixed Design

combines between group and within subjects design by including at least one between groups IV and one within subjects IV
*common in studies involving measuring the DV across trials of time


Factorial Design

- when a study includes two or more IVS, provides more thorough information about the relationships among variables by allowing an investigator to analyze the main effects of each IV as well as the interaction between IV.