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PSYS 284 Research Methods Chapters 12, 8, and 9

by: Kaitlynn Bennett

PSYS 284 Research Methods Chapters 12, 8, and 9 Psys 284-002

Marketplace > Ball State University > Psys 284-002 > PSYS 284 Research Methods Chapters 12 8 and 9
Kaitlynn Bennett
Research Methods in Psychological Science

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Chapter 12 covers important decisions that need to be made for an experiment, the job of both the dependent variable and the dependent variable Chapter 8 covers internal and external validity of ...
Research Methods in Psychological Science
Psychology, research methods
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This 0 page Bundle was uploaded by Kaitlynn Bennett on Thursday January 28, 2016. The Bundle belongs to Psys 284-002 at Ball State University taught by Mittleman in Summer 2015. Since its upload, it has received 127 views.


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Date Created: 01/28/16
EXAM 2 NOTES Ch 12 Important decisions to make Subjects pulled from larger population 0 become a sample 0 sample is either control group or experimental group 0 Importance of subjects Direct impact on who you can generalize your results back to advantage of randomly choosing subject the sample looks like the population 0 population contains some sort of subject that will cause there to be difference between them and another subject to reduce this I tell sample to think or act a certain way to generalize them back to the population ex telling subjects I would like you to lie to me for the purpose of generalizing give subjects some sort of written or verbal instructions 0 ensure that there is no variabilityin sample is to give EVERYONE the same set of instructions be consistent EX if you approach everyone in the same building but sometimes your in a bad mood and sometimes your in a good mode this will produce variability Independent Variable jobe of IV motive force that is going to cause movement of the dependent variable 0 Population sample control sample and experimental sample Look at in terms of DV before experiment even happens l the 2 groups should maintain similarities because they have been randomly assigned to a control group or an experimental group Does the IV work 0 IV in uenced DV if once the IV is applied to experimental group there is a movement in the DV 0 IV has no in uence on DV if once the IV is applied to the experimental group there is no movement in the DV 0 OR the IV was too weak to in uence the DV Choose IV and how much of it will be applied Different level of the IV 0 Control Group 0 Experimental level 1 0 Experimental Level 2 0 Experimental Level 3 Advantage of using multiple levels of IV it becomes a more complex experiment 0 What is the relationship between the IV and DV 0 Increasing dosage of IV could affectthe DV in different ways 0 The dosage of one experimental group could not be strong enough to have an in uence on the DV 0 Take to many dosages it could have and adverse affects one is to weak or three is too much Hard to see with only one level of IV Dependent Varibale Job of DV Sensitive to the in uence of the IV Construct something that exists in our heads that explains a phenomenon Ex Depression you can t see it weigh it can t touch it BUT it s there 0 Measure Happiness Motivation Hopelessness Energy level Eating behavior Ability to concentrate 0 Do you think we will get the same results for each DV DV may not be sensitive to the IV Think about level of match up of IV and DV Think about the amount of IV and DV IV didn t work IV not strong enough DV not sensitive Type of Designs Between subjects Two or more groups Control group and experimental group 0 Advantage Random selection and assignment l assumes groups are equivalent to begin with o Disadvantages lf groups aren t equivalent to begin with extraneous variables awed experiment and won t be able to draw conclusions 0 Requires you to test before in order to gure that out To many groups Within subjects One group measured twice 0 Advantages Fewer subjects 0 Disadvantages Extraneous variables 0 Time effect separation between the time of testing could cause something to happen that would cause a different in DV 0 Practice effect give same test before and after IV there is a possibility that the subject learns form the rst test and uses this knowledge 218 Internal Validity of an experiment Internal validity the degree to which values of the DV are free from the in uence of extraneous variables what we strive for in an experiment 0 Should ask quotcan you think of any other variable that may have caused the difference between groups other than the treatment 0 If so what can we do to eliminate these extraneous variables from occurring 0 When the experience is nished can we conclude that we believe and have con dence in the results Ex two groups with different results 0 Maybe the groups are different form one another therefore results won t be similar no matter the treatment 0 High good internal validity Unlikely that extraneous variables played a role in the results con dence in the result 0 Ruling out that systematic group differences 0 Low bad internal validity we did the experiment and the groups weren t selected randomly 0 making it possible that the groups are systematically different Terminology Extraneous variables directly affect the behavior but have nothing to do with the IV threats to internal validity as extraneous variables go up internal validity goes down vise versa Threats to internal validity 1 History threats Proactive history apply when there are 2 or more groups Apply to all learned or inherent differences subjects bring to a study Are all these differences equivalent between two group Ex education levels could affect responses to experiment HOWEVER hair color is less likely to effect results Try to balance these differences 0 Group of interest those characteristics that could actually affect results 0 random selection highly likely that groups will be similar good 0 Retroactive history two or more measurements events that occur in between measurements applies to any number of groups 0 Control group is IMPORTANT Example Point 1 Randomly select two groups randomly assign to treatment and control group and randomly gave subjects a pretest quot what does this sayquot the groups were equal to begin with Point 2 Pretest and posttest are the same control group didn t change means nothing caused the subjects to stay NO retroactive history effects Point 3 control and treatment group are different random selection assignment worked our control and our treatment group are signi cantly different and our treatment worked lcaused DV to move and control group is changing there is an in uence of extraneous variables Conclusion 0 Exposing these groups signi cantly change their attitudes about In addition there were in uence of extraneous variables but we are unaware of these treats 223 CH 8 ValidityControl 2 Maturation only applies when using very young or very old subjects o In both cases it refers to age related changes 0 If testing the young over time it may not be in response to IV but the fact that they are maturing getting older 0 If testing the elderly the subject may have a response due to losing cognitive ability over time rather than the IV having an effect 3 Testing process that occur when you repeatedly test subjects 0 Test 0 Practice 0 Fatigue only occurs when tested repeatedly in a very sort time 0 Causes scores response to go down due to getting tired Ex pre test and post test on how much they know about care maintenance 0 The control group tells us there is a threat to internal validity By incorporating another group and only post testing them you can nd if it is retroactive or proactive history threat 4 Selection anything other than random selection will yield non homogenous groups 0 Before an experiment ever occurs once the groups are selected NON randomly groups are guaranteed to be non similar even before the experiment occurs Can still have partial similarity ex age BUT always open to threats of validity without random selection 5 Subject Mortality loss of subjects 0 As you loose subjects you loose data 6 Experimenter bias experimenter has knowledge of group membership and treats the groups differently Possibility that experimenters behavior can alter scores on IV 7 lnstrumentation calibration of an instrument 0 Ask question quot could the increase because caused by the sensitivity of the instrumentquot 225 External Validity of an experiment External Validity ability to generalize your results to a larger population things that can effect the DV Ability to generalize is depend on modi cation of 0 Demographics of the sample 0 Does the sample thinklike the population High external validity ability to generalize GOOD 0 What we strive for 0 Con dence in generalizing our results Low external validity little possibility to generalize Good experiment characteristics 1 High internal validity 0 Con dence in results 0 Dif cult to attribute any of the experiment to extraneous variables 2 High external validity 0 Ability to generalize the results due to demographics being the same in sample and population 3 It answers the question you are asking Reactivity in research A Hawthorne effect in uence by experimenter that could change the behavior of the subjects 0 Doesn t effect demographics but the thinking of the subjects 0 Experimental group Pretesting Experimental group gets a pre and a post test and the control group gets the post only 0 Case of hawthorn effect l changes peoples expectancies by telling them they are in the control or the experimental group 0 Single bind The experimenter doesn t know group membership If the experimenter doesn t know they can t alert the groups Changes thinking of subjects l threat to internal validity B Evaluation apprehension concern on the subjects part about the impression they leave with the experimenter C Demand Characteristics characteristics of the experimenter that eicit certain responses in the subjects 0 Experimenters express their interest or non interest in an experiment Selection anything other than random selection will yield a sample that is different demographically from the population dual threat 0 Internal validity If you don t seect randomly they will have systematic differences l the groups weren t homogenous to being with 0 External validity Sample does not resemble the population out of which it was drawn Subject mortality subject loss 0 As we oose subjects out of sample question whether the sample is still representative of the population 0 Threat 0 Internal validity testing students over period of time could see selective loss of lower scores mean of scores will change 0 Subject mortality will cause changes to DV 31 Validity of the DV 1 Construct validity how well does the DV capture the construct something that exists in our heads about what something is abstract concepts Ex intelligence and depression nothing physical like weight will effect intelligence 0 New IQ test really measure intelligence compare to existing measures of intelligence 2 Content Validity how well the DV measures current performance Ex current levels of performance 3 Predictive validity how well the DV predicts future performance Ex Taking tests like SAT are supposedly done to predict how well you Will do in college future levels of performance Reliability of the DV Reliability applies to its consistency of the measurement Ex IQ test give to people on one day then days later the test should show approximately the same results GOOD 0 High reliability has consistency High construct validity Measures what it is suppose to measure BAD Low in reliability 0 Low in construct validity CH 9 Experiment Briefs 1 Hungry Cats IV food deprivation DV aggression Do you believe the results 0 No comparison to hungry cats that are aggressive By comparing to non hungry cats with less aggressive 3 DV number of syllables recalled IV time spent studying Do you believe the results 0 Scores increased after having practice over 3 days 0 Time spent studying varied and should have been the same amount of practice time for all three groups o If changed there are no relevant extraneous variables involved 5 DV blood pressure IV bio feedback Do you believe the results 0 Few participants 0 We don t know if they changed their diet Could effect the DV independently form the IV 0 No regression towards mean of population 0 No change in the control group then bio feedback works 0 Anytime there is a change in the control group some extraneous variable is causing them to change


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