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Psychology (9,697)
PSYB01H3 (581)
Anna Nagy (283)
Chapter 9

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Anna Nagy

Chapter 9- Conducting Experiments SELECTING RESEARCH PARTICIPANTS - The method used to select Ps can effect external validity (the extent to which results from a study can be generalized to other populations/settings) MANIPULATING THE INDEPENDENT VARIABLE - To manipulate it, you have to construct an operational definition of the variable Setting the Stage - Informed consent - Experimental setting must seem plausible to the Ps, nor are there any clear-cut rules for translating conceptual variables into specific operations - Exactly how the variable is manipulated depends on the variable and the cost, practicality, and ethics of the procedures being considered Types of Manipulations - Straightforward manipulations- presenting written, verbal or visual material to Ps o Manipulate variables with instructions and stimulus presentations o Verbally, written, videotape or with a computer - Staged manipulations- need to stage events during the experiment in order to manipulate the independent variable successfully o Also called event manipulation o Used for 2 reasons:  Researcher may be trying to create some psychological state in the Ps  Necessary to simulate some situation that occurs in the real world o Commonly uses confederates Strength of the Manipulation - Simplest experimental design has 2 levels of the independent variable o Making the manipulation strong as possible, but has 2 considerations:  External validity- may not happen in real life  Ethics- manipulation should be strong within ethical boundaries Cost of the Manipulation - Straightforward is less expensive MEASURING THE DEPENDENT VARIABLE Types of Measure - Self-reports- used to measure attitudes, emotional states, attributions, confidence and other aspects of human behaviour o Rating scales with descriptive anchors (endpoints) are used - Behavioural measures- direct observations of behaviours o Like self-reports, measurements of infinity behaviours are possible  Rate of behaviour- number of times a behaviour occurs in a time period  Reaction time- how quickly a response occurs after a stimulus  Duration- how long a behaviour lasts - Physiological measures- recordings of responses of the body o Galvanic skin response (GSR)- general emotional arousal/anxiety o Electromyogram (EMG)- muscle tension for stress o Electroencephalogram (EEG)- electrical activity of brain cells o MRI- image of brain structure o fMRI- scan areas of the brain while a P does a physical/cognitive task Sensitivity of the Dependent Variable - Dependent variable should be sensitive enough to detect differences between groups - Ex. Do you like this person? Can't be answered with a yes or no, should be answered with a 7 point scale - Ceiling effect- the independent variable appears to have no effect on the dependent measure only because Ps quickly reach the max performance level - Floor effect- task is so difficult that no one performs well Cost of Measures - Pencil and pen self-report measures are cheap - Measures that need trained observers or equipment can be costly - Physiological recording devices are expensive - Researchers need resources from the uni or outside agencies to carry out their research ADDITIONAL CONTROLS Controlling for Participant Expectations - Demand characteristics- any feature of an experiment that might inform Ps of the purpose of the study o When Ps form expectations of the purpose of the study, they will do what's necessary to confirm the hypothesis o To control for this, use deception and filler items on a questionnaire - Placebo group- receive a pill or injection of a harmless substance o Pla
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