RS: Ch 9 Experimental control
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| What is the most rigorous form of scientific investigation, and the best process for testing hypotheses | THE EXPERIMENT
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| The purpose of the Experiment: | The purpose is to support a cause-and-effect relationship
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| What is the Experiment: | Researcher systematically introduces changes into natural phenomenaObserves consequences of those changesMust have sufficient control over ex situation to be a true exThose variables that are not able to be controlled are considered limitations
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| One drawback – to the Experiment: | if too much control can’t apply to the real world
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| Extraneous variables | Are considered confounding variablesAny factor that is not directly related to the purpose of the studyNot related but affects the DVCan be extrinsic factors or intrinsic factors
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| If an Extraneous Variable is not controlled it can exert a ________ | can exert a confounding influence on the IV
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| Experiments are designed to control for________ | designed to control for these confounding influences
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| Extrinsic Factors: | factors that emerge from the environment and the experimental situation
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| Intrinsic Factors: | represent personal characteristics of the subjects of the study.
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| Confounding | is the contaminating effect of extraneous variable on the interpretation of the relationship between independent and dependent variable.
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| ESSENTIAL CHARACTERISTICS OF A true EXPERIMENT | The independent variable must be manipulated by the researcherThe participants must be randomly assigned to groupsA control group must be incorporated within the design
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| MANIPULATION OF VARIABLES | Researcher deliberately imposes an experimental condition (IV) on at least one group of participantsParticipants are assigned to different levels of the IV
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| The the Researcher does what to the active variable : | MANIPULATES
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| The the Researcher does what to the attribute variable: | does NOT manipuate
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| Active variable: | is an independen variable with levels that can be Manipulates and assigned by the researcher
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| Attribute variable: | is an independent variable with levels that cannot be manipulated or asigned by the researcher, but hat represent the subject characteristics (such as age or sex)
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| RANDOM ASSIGNMENT | Each participant has an equal chance of being assigned to any groupAssignments are independent of personal judgment or biasGroups are then theoretically considered “equivalent”
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| Def of Random Assignment | is the assignment of subjects to groups using probability methods, where every subject has an equal chance of being assigned to each group.
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| Equivalence: | means any differenes between groups are due to chance alone, this way inter-participant differences should balance out
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| Randomization is an issue of | probability!Done by use of random numbers table or computer
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| Use of control group is the most effective way for ruling out | extraneous effects
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| The control group usually receives | no treatment or the “standard” treatment
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| The treatment group receives | the manipulation
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| Double-blinded study: | is an experiment in which both the investigator and the subject are kept ignorant of group assignment
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| Single-blinded study: | an experiment in which either the investigator or the subject is kept ignoratnt of group assignment, not both Ronda- only experimenter is blind
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| CONTROLLING INTER-PARTICIPANT DIFFERENCES | Selecting homogeneous participantsBlockingMatchingSubjects as own controlAnalysis of Covariance (ANCOVA)
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| Homogeneous participants | Selected based on homogeneous characteristicsExample:Gender or age makes a differences
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| blocking | Builds the attribute variables into the experimental design as an IVExample:If age makes a difference have different age groupsRandomly assign participants within the group – randomized block design
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| Block | is a level of an attribute variable in which subjects are homogeneous on a particular characteristic
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| Blinding | are techniques to reduce experimental bias by keeping the subjects and/or investiagators ignorant of group assignmetns and research hypotheses
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| Confounding Variable: | a variable taht is more likely to be present in one group of subjects than another, and that is related to the outcome of interest, thereby potentially "confounding" interpretation of the outcome.
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| what is matching, give some examples | Participants “matched” based on specific characteristic(s)Example:AgeSexDisease
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| participants as own control | All participants receive all levels of the IVRepeated measures design
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| ANALYSIS OF COVARIANCE | A statistical analysis that eliminates influences of extraneous factorsThese extraneous factors become the covariatesThe process makes covariates artificially equivalent across groups
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| Analysis of covariance ( ANCOVA) | uses a statistical technique to equate groups on extraneous variables. ANCOVA is based on concepts of analysis of variance and regression.
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