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Lecture 6

2012.10.18 PSYB01H3 Week 6 Lecture_Outline_experiment.docx

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Department
Psychology
Course
PSYB01H3
Professor
Connie Boudens
Semester
Fall

Description
2012-10-18 Lecture 6 Experiments A demonstration: the taste test before Coca Cola Vs Pepsi - Not good experiment because many things she talked may affect the results of the experiment - Reminding of relationships b/t variables like height and weight; the pet ownership and wealth o Eating bbreakfast are positively related to academi performance in school age children o Eating disorders and wtching soap in teenaged famales - But, does the above mean that eating breakfast causes better academic performance, or that watching soap operas causes eating disorders? - The correlation only tells you the two are correlated but not the causal Problems with establishing causality in correlational research  Direction of influence problem: there are may be two different directions o For ex: class attendance and grades  It could be higher attendance make a higher grade, but also, the students with higher grade are more likely to attend classes  Third variable problem o For ex:positive mood and charitable donations  These two are positively correlated  But there may be a 3 variableslike the day after they got the payment are more likely to donate o Ice cream and drdwning:  The 3 variable is high temperature  In some cases, maybe the two above problems come together: problems with both direction of influence and third variables. o For example: depressed mood and impaired sleep, and also family conflicts Three things needed to establish causality  Temporal order must be correct: temporal ordercasue has to come before outcome  Variables have to covary: they have to in some way varying together  No other variable is causing the outcome: like in the expereiment of Coca, the different ice cold temperature of the two drinks, and this is the “other” variables How experiments allow you to do this  Hold all variables constant o May still have influence, but the influence will be the same on all participants  Use random assignment for anything that you cannot hold constant o in the random assignment to assign different ppl in group 1 or 2; the ppl have the equal opportunity to put in one condition or another  Present i.v. first to see what happens after: b.c the IV causes the DV  Present i.v. carefully and consistently, measure the d.v. rigorously(strictly) Extraneous vs confounding variable - Confounding variables: type of extraneous variables - Confounding variables are related to the IV o Ex: temp of drink confounded with type of drink, length of relationship confounded with gaze behaviour o Ex: when man has to apologize for, when the man is doing this, the woman was gazing him. Are we able to predict whether she will forgive him by calculating the length of time that she was looking at her; could we estimate the possibility based on the time she spent on looking at him; the problem was the confound was, the new lovers spending more time looking at each other. So that gazing is not a good way to tell whether she will forgive him. Basic experimental design  One i.v. two levels o Experimental group/the treatment group: experimental stimulus administered –in other words, something happens to this group o Control group :no experimental stimulus applied but all other things should be same as experimental group  One d.v. Experimental Group Administer the IV Measure the DV Control group Measure the DV Ex: effect of noise on memory Experimental group Memorize words in a loud room Measure performance on memory task Control group Memorize words in quiet room Measure performance on memory task - There is a problem here: ppl may remember things in different ways: like someone prefer memorizing in loud or quiet circumstance; so you need the random sampling Pre-test- posttest design - Pre-test: doing a test before the experiment. - Reasons for pre-test  Make sure groups are actually equivalent: like to make sure the average of ppl to memorizing ability are same  Identify people with high/low pre-existing characteristics to figure out that whether there is interaction o Ex: looking at effects of noise on introverts Vs extraverts  In case of mortality: not ppl dying/dropping out the experiment especially in a long time experiment; it is not a problem if the types of ppl dropping in two groups are same o Ex: the ppl don’t like crowd may be leaving and the experimental group ppl may become as the ppl who do not mind the crowd and they are doing good in the experiment as the ones in the quiet room  Measure change in each individual: especially when teaching something—measure the ability before and measure the ability afterwards Independent groups vs. repeated measures  Independent: all p’s exposed to one level of i.v.  Repeated measures: all p’s exposed to all levels of i.v. o less participants o No individual differences o Order effects: the problems of order effect  Order Effects: People behave differently in second conditio
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