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Lecture 8


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PSYC 2230
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RESEARCH METHODS LECTURE 8 THURSDAY, JULY 19TH, 2012 TOPIC: EXPERIMENTAL RESEARCH I EXPERIMENTAL RESEARCH ➔ The research design you choose is based on the questions you ask and ho you define your variables ➔ IV is manipulated (independent variable) ➔ DV is measured (dependent) ➔ Thee is control over extraneous variables ➔ Acasual relationship between the IV and DV can be established ➔ Independent variable → manipulated by the researcher ex. Brightness of a lamp, loudness of a tone etc, has at least two different conditions. Can see if your performance increases or decreases in each situation given. Example: two versions of the exam → could be interested in seeing if the coloured paper would have an impact on grades. Coloured paper (independent) grade results (dependent). If you had pink, blue and yellow paper that would be 3 independent levels ➔ True experiment → we test the effects of a manipulated IV ➔ Sometimes subject variables are used → characteristics of a participant themselves (gender, age, intelligence, personality). Cannot be manipulated experimentally. Cannot make causal statements about the manipulation between variables. ➔ Dependent variable → measured by the experimenter, used to determine the affect of the IV. Usually measure several Dvs. If hypothesis is correct → different values of IV should produce changes in DV. Example: depression could be an IV or DV depending on the research question. Example: depressed people are less satisfied in life then non depressed individuals (IV). Gender and whether females report more depression than males (DV). ➔ Know what the DV and IV is, know how many levels there are and know whether it is a subject variable or manipulated variable for test questions ➔ Subject variable (cannot infer causality) ➔ Example: weight is the IV (whether one is normal or overweight would be two levels) ➔ Casual Inferences → there has to be a relation between your IV and your DV known as covariation. Time-order relationship → cause perceives effect (measure IV first then DV). Elimination of plausible alternative causes ➔ Extraneous Variables → factors not of interest to the researcher but might influence the behaviour that is being studied ➔ Confoundings → variables that change systematically across the different conditions of the IV. Ex. Experimental group =men control group =women. Sex of participant is confounded with IV ➔ Any result found must be interpreted cautiously CONTROLTECHNIQUES ➔ Elimination ➔ Holding Conditions Constant → only thing we allow to vary across our groups is the IV; everything else should be the same for the groups in the experiment ➔ However there are some variables you cannot keep constant such as characteristics of your participant. You can recruit a certain age range to keep that constant so to speak ➔ Balancing → make sure that, on average the participants in each condition are essentially the same before the experiment begins ➔ You will use random assignment to condition BIASASACONFOUNDING FACTOR ➔ Participant bias → good subject role (try to help researcher, might try to conform their behaviour to your hypothesis), negativistic role (sabotage study), apprehensive (might feel uncomfortable about being evaluated and as a result they try to make themselves look as normal as possible) ➔ Ways to eliminate this: might include a manipulation check at the end of the study asking them what they thought the study was about ➔ Experimenter Bias → experimenter's expectancies influence their behaviour toward participants in different conditions (give subtle cues on how to behave or respond) ➔ Potential remedy: double blind experiment: keeping experimenters and observers unaware of the hypotheses or expected results (may hire a research assistant to run the study instead of the head person → might not know what condition each person is in) EVALUATING THE EXPERIMENT ➔ Internal Validity → extent to which one can accurately state that the IV produced the desired effect ➔ Should be a concern during the design phase of study ➔ External Validity → extent to which findings from an experiment can be generalized to individuals, settings, and conditions beyond the scope of a specific experiment ➔ Would the same findings hold true for different participants, occur in different settings or other times? ➔ Other populations → Research with university students often criticized because of low external validity ➔ sears → university students → formulated sense of self, stronger tendency to comply with authority, less stable peer relationships, high intelligence ➔ Volunteer bias → (Rosenthal and Rosnow) → more educated, higher social class, more intelligent, more approval need, more social, more “arousal seeking”, more likely female, less authoritarian, less conforming, more altruistic, more self-disclosing, tend to be younger ➔ Environmental generalizations applying the results from an experiment to a situation or environment that differs from that of the original experiment. Can we generalize to different countries and cultures? Lab → real world example → studying list of words in lab.Any relevance to studying for an exam? ➔ Temporal generalizations → extent to which the results would generalize to other times example: smoking cessation study in the 60s and 70s would likely produce very different results to a study conducted in the 2005 ➔ Statistical Conclusion validity → not mentioned often, difficult to assess. ➔ Extent to which the researcher uses statistics properly and draw appropriate conclusions ➔ Can be reduced if: wrong analysis performed or violate some assumptions, selectively reports some analyses ➔ Internal versus External → tends to be an inverse relationship ➔ Internal validity increased and external decreased THREATS TO INTERNALVALIDITY ➔ History → outside events or occurrences that affect responses ➔ Effect of the IV on the DV cannot solely attributed to the IV ➔ Example: weather, news reports, and time of day ➔ Cannot say with confidence that changes of your DV were because of your IV ➔ Are people more charitable to victims in a natural disaster? This could be influenced by the news report. Would include whether these participants were run before or after the event to know if this is true (do people become more charitable after the news report and event?) ➔ Maturation → changes in the internal conditions of the participant that occurs over as a function of the passa
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