Experimental Design PSYC-31574-003
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This 2 page Class Notes was uploaded by Amy Turk on Saturday April 16, 2016. The Class Notes belongs to PSYC-31574-003 at Kent State University taught by Dr. Tanjeem Azad in Spring 2016. Since its upload, it has received 10 views. For similar materials see Research Methods In Psychology in Psychlogy at Kent State University.
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Date Created: 04/16/16
EXPERIMENTAL DESIGN Within Subjects ● A single group of participants serves in all conditions of the experiment ● Advantages ○ Eliminates need for random assignment ○ More powerful ○ Fewer participants needed ● Disadvantages ○ Order effects = when the sequence or order of experimental conditions of the IV influences the measure ■ May threaten the internal validity ○ Practice effects = responses improve because participants have completed the DV several times ○ Fatigue ■ Solutions = make task more interesting, keep tasks brief ○ Sensitization = subjects figure out the experiment and respond differently as it progresses ■ Solution = use deception ○ Carryover effects = the effects of condition A are still lingering when condition B begins and those lingering effects may influence behavior during condition B ■ Solutions = lengthen the time between conditions, use strategies that clear the effect of one condition before exposing participants to the next condition ● Counterbalancing = presenting levels of the IV in different orders to different participants Threats to Internal Validity ● Biased assignment ● Differential attrition = people in one condition drop out at a higher rate ○ No longer have the benefit of random assignment ● Pretest sensitization = taking a pretest may sensitize individuals to take the independent variable so they react differently than if they had not been pretested ● Stimulus materials = differences between stimuli other than the intended IV can alter DV ● Participant effects = demand characteristics ○ “Good subject effect” ○ If people know the purpose of the study, they may be more co-operative ○ Evaluation apprehension = being evaluated can make us act differently than normal ■ Ex. nervous, try harder, etc. ● Internal validity = experimental expectancy effect = if the experimenter knows which condition participants are in, their expectations about outcome of study can influence his/her treatment of them ○ Ex. Rosenthal effect = two groups of students tested maze running performance of rats ○ Maze bright vs maze dull rats = but all rats were from the same source ○ Maze bright rats ran the maze faster ○ Students’ beliefs and expectations unconsciously influenced performance of rats Solutions to Participant and Experimenter Effects ● Cover story ○ Conceal purpose of study ○ Reduces participant effects ● Blind study ○ Participants don’t know their condition, so they are less likely to know what’s expected of them ○ Single blind or double blind
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