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Carleton University
PSYC 2001
Vessela Stamenova

Psychology Review Midterm Test: November 11, 2011 Chapters: 7-11, 15 11 & 15 separate Chapter 7: The Experimental Research Strategy Cause and Effect Relationship An experiment (true experiment) attempts to establish a cause-and- effect relationship by demonstrating that changes in one variable are directly responsible for changes in another variable. Experiment Establishes a cause and effect relationship between two variables One variable is manipulated (independent) Second variable is measured (dependent) Changes in the dependent variable are caused by the changes in the independent variable Manipulating the independent variable and seeing its effects on the dependent variable allows a researcher to determine a cause and effect relationship Basic Elements of a True Experiment An experiment contains four basic elements 1.Manipulation Of the Independent variable You have to manipulate the levels of the independent variable in the different groups 2.Measurement Of the dependent variable Measure the effects of the IV on the DV 3.Comparison The scores of Group1 on dependent variable are compared to scores in Group 2 If difference observed, then we have a cause and effect relationship Comparing the effects of different levels of IV on the DV 4.Control All variables that may inuence the independent or dependent variable are controlled Must make sure that all the possible (extraneous) variables that may have inuence are controlled for, as best as possible. Terminology -3rd Variable Problem: There could be a third variable causing changes in * 1 the two variables that you are observing, an extraneous variable is inuencing results Causation and the Directionality problem Establish relationship between variables Difficult to determine which one causes the other A B B A Directionality Problem: hard to know which variable is causes the other (which variable is the cause and which is the effect Basic Elements of a True Experiment Manipulation Allows researchers to determine directionality Helps control the inuence of extraneous variables In an experiment, manipulation consists of identifying the specic values of the independent variable to be examined and then creating a set of treatment conditions corresponding to the set of identied values. Primary purpose of manipulation is to allow researchers to determine the direction of a relationship. (Which is cause and which is effect) Control Control All variables that may inuence the independent or dependent variable are controlled Elimination of confounding variables Vary systematically with the independent variable Inuence the dependent variable Extremely important to control confounding variables so results arent inuenced Vary systematically with the independent variable - difficult to see, also inuence the dependent variable Threats to Internal Validity Environmental Variables - Make sure the environment in which the test takes places stays as consistent as possible Individual Differences - Make sure individuals with similar characteristics are divided as evenly as possible between the groups Time-related Variables - Balance the sequencing of the tests equally across the groups of participants Dealing with Extraneous Variables Holding constant * 2 Holding constant-by standardizing the environment and procedures, most environmental variables can be held constant Matching values across treatment conditions Matching: the assignment of individuals to groups so that a specic variable is balanced or matched across the groups. (denition in textbook) Randomization Can control for a wide variety of variables Randomization: is the use of a random process to help avoid a systematic relationship between two variables. Randomization can also be used to control environmental variables. Example: establishing which time of day a treatment is given by ipping a coin. Thus, time of day is randomly distributed across treatments and does not have a systematic effect on the outcome. Matching - a way of randomization, but not true randomization Randomization - in each study, there will be thousands of extraneous variables; you can control for some major/important ones, but there are many you may not even be aware of; randomization makes sure the extraneous variables is randomly distributed among the groups and you hope it takes care of the inuence on your results Control Groups Experimental group Treatment condition Control group No-treatment control group wait-list group Placebo Control Group The placebo effect The term control group refers to the no-treatment condition in an experiment. 1.Placebo group must appear to be experiencing the exact same thing that the treatment group is experiencing 2.Wait-list groups are not used as commonly today; they are tested, then do something for a while (while waiting) and are tested again A no treatment control group is a condition in which the participants do not receive the treatment being evaluated The placebo effect refers to a response by a participant to an inert medication that has no real effect on the body. The placebo effect occurs simply because the individual thinks the medication is effective. Manipulation Checks * 3 An additional measure to assess how the participants perceived and interpreted the manipulation and/or to assess the direct effect of the manipulation. An explicit measure of the independent variable . E.g. not only diagnosis but additional testing Post study questionnaire Participant manipulations Subtle manipulations Simulations Placebo groups A manipulation check directly measure whether the independent variable had the intended effect on the participant Participant Manipulations - putting some people in a high stress situation and others in a low stress situation Subtle Manipulations - changing the lighting slightly for one group and seeing if there is any effect Simulation - such as the Stanford Prison Experiment (it looked like a prison but really wasnt) Placebo - appears to be something but is not Lab VS. Field Research Lab studies Good internal validity Poor external validity Field studies Poor internal validity Good external validity Lab Studies - can control for most extraneous variables - hard to say if the behaviour seen in the lab is the same behaviour that people will engage in outside of the lab Field Studies - can see how people actually behave - hard to control for some extraneous variables Simulation Studies Simulation: the creation of condition within an experiment that simulate or closely duplicate the natural environment in which the behaviours being examined would normally occur Mundane Realism: supercial, physical characteristics of the simulation; little effect on external validity Experimental Realism: psychological aspects of the simulation; participants are completely immersed in the manipulation and forget that they are in an experiment * 4
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