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Psychology (9,545)
PSYB01H3 (585)
Chapter 9

CHAPTER 9.docx

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University of Toronto Scarborough
Connie Boudens

CHAPTER 9: CONDUCTING EXPERIMENTS SELECTING RESEARCH PARTICIPANTS -participants or subjects must somehow be selected -method used to select participants has implications for generalizing the research results -most research projects involve sampling research participants from a population of interest -popln is composed of all the individuals of interest to the researcher -samples may be drawn from the popln using probability or nonprobability sampling techniques -when important to accurately describe popln, must use probability sampling -much research more interested in testing hypotheses about bhvr; focus of study is relationships b/w variables being studied and testing predictions derived from theories of bhvr -participants may be found in easiest way possible using nonprobability haphazard or “convenience” sampling methods -nothing wrong with such methods as long as it is realized that they affect ability to generalize results to some larger popln -evidence supports view that we can generalize findings to other poplns and situations -sample size also needs to be determined -increasing sample size increases likelihood that results will be statistically significant b/c larger samples provide more accurate estimates of popln values MANIPULATING THE INDEPENDENT VARIABLE -to manipulate the IV, you have to construct an operational def’n of the variable -IV and DV must be introduced w/in context of total experimental setting “setting the stage” Setting the Stage -have to do 2 things: 1) provide participants with informed consent info needed for study 2) explain to participants why experiment is being conducted -rarely want to tell participants actual hypothesis; sometimes rationale give completely truthful -may try to confirm hypothesis if they known what you’re studying -or may try to look good by behaving in most socially acceptable way -if deception is necessary, have a special obligation to address deception when you debrief participants at conclusion of expt -no clear-cut rules for setting stage except that the experimental setting must seem plausible to participants -no clear-cut rules for translating conceptual variables into specific operations -exactly how variable is manipulated depends on variable and cost, practicality and ethics of procedures being considered Types of Manipulations Straightforward Manipulations -researchers usually able to manipulate variable with relative simplicity by presenting written, verbal, or visual material to participants -straightforward manipulations manipulate variables w/ instructions & stimulus presentations -stimuli may be presented verbally, in written form, via videotape, or w/ computer -most memory research relies on straightforward manipulations -researchers vary difficulty of material to be learned, motivation levels, way questions are asked, characteristics of people to be judged & variety other factors in straightforward manner Staged Manipulations -sometimes necessary to stage events that occur during expt in order to manipulate iv -called staged or event manipulation -most frequently used for 2 reasons: 1) researcher may be trying to create some psychological state in participants (anger, frustration, temporary lowering of self-esteem) 2) staged manipulation may be necessary to stimulate some situation that occurs in real world -staged manipulations frequently employ a confederate (sometimes termed an “accomplice”) -confederate appears to be another participant in an expt but is actually part of manipulation -may be useful to create a particular social situation -may be used in field expts as well as lab research -Asch demonstrated how easy it’s to produce conformity—participants conformed to unanimous majority on many of the trials even though the correct answer was clear -staged manipulations demand great deal of ingenuity and even some acting ability -they’re used to involve participants in an ongoing social situation which the individuals perceive not as an experiment but as a real experience -researchers assume result will be natural bhvr that truly reflects feelings and intentions of participants -all for great deal of subtle interpersonal communication that’s hard to put into words -make it difficult for other researchers to replicate expt -complex manipulation difficult to interpret -easier to interpret results when manipulation is relatively straightforward Strength of the Manipulation -simplest experimental design has 2 levels of IV -general principle: make manipulation as strong as possible -strong manipulation maximizes diffs b/w 2 groups and increases chances that IV will have statistically significant effect on DV -strong manipulation particularly important in early stages of research when researcher is most interested in demonstrating that a relationship does in fact, exist -if early expts reveal relationship b/w the variables, subsequent research can systematically manipulate other levels of IV to provide more detailed pic of relationship -principle of using strongest manipulation possible should be improved by at least 2 considerations: 1) strongest possible manipulation may involve a situation that rarely occurs in real world 2) ethics: a manipulation should be as strong as possible w/in bounds of ethics Cost of the Manipulation -researchers who have limited monetary resources may not be able to afford expensive equipment, salaries for confederates, or payments of participants in long-term expts -more time consuming for manipulation in which participants must be run individually -manipulation that uses straightforward presentation of written/verbal material is less costly than a complex, staged, experimental manipulation MEASURING THE DEPENDENT VARIABLE Types of Measures -DV in most expts is 1 of 3 general types: self-report, behavioural, or physiological Self-Report Measures -self-reports can be used to measure attitudes, liking for someone, judgments about someone’s personality characteristics, intended behaviours, emotional stress, attributions about why someone performed well or poorly on a task, confidence in one’s judgments -rating scales with descriptive anchors are most commonly used Behavioural Measures -direct observations of behaviours -measurements of an almost endless number of behaviours are possible -sometimes researcher may record whether or not a given behaviour occurs -researcher must decide whether to record # of times a behaviour occurs in a given time period—rate of a behaviour; how quickly a response occurs after a stimulus—reaction time; or how long a behaviour lasts—duration -decision of which aspect of behaviour to measure depends on which is most theoretically relevant for study of particular problem -or which measure logically follows from IV manipulation -sometimes nature of variable being studied requires either a self-report or bhvrl measure -for many variables, both self-reports and behavioural measures could be appropriate -when both options are possible, a series of studies may be conducted to study the effects of an IV on both types of measures Physiological Measures -recordings of responses of the body -galvanic skin response (GSR): measure of general emotional arousal and anxiety; measures the electrical conductance of the skin which changes when sweating occurs -electromyogram (EMG): measures muscle tension and is frequently used as measure of tension or stress -electroencephalogram (EEG): measure of electrical activity of brain cells; can be used to record general brain arousal as a response to diff situations, activity in diff parts of brain as learning occurs or brain activity during diff stages of sleep -others avail such as temperature, heart rate and info that can be gathered from blood or urine analysis -MRI has become increasingly important tool for researcher in behavioural neuro -MRI provides image of brain structure of an individuals -allows scientists to compare brain structure of individuals with particular condition w/ those w/out the condition -functional MRI (fMRI): allows researchers to scan areas of brain while research participant performs physical or cognitive task -provides evidence for what brain processes are involved in these tasks Sensitivity of the DV -dv should be sensitive enough to detect diffs b/w groups -sensitivity is particularly important when measuring human performance -sensitivity: ability of a measure to detect diffs b/w groups -sometimes task is so easy that everyone does well regardless of conditions that are manipulated by IV -ceiling effect: IV appears to have no effect on the dependent measure only b/c participants quickly reach the maximum performance level -floor effect: task is so difficult that hardly anyone can perform well Multiple Measures -often desirable to measure more than one DV -o
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