Lecture 8 11.23.09

Lecture 8 11.23.09 - 11/23/09 Psych 100B Lecture 8 Using...

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11/23/09 Psych 100B – Lecture 8 Using observational research methods to incorporate them into a true experiment but on the other hand, if we are doing pure observational research using the same methods, you cannot assume you are doing a true experiment. Quasi-experimental research Threats are alternate explanations for the results obtained from quasi-experimental research. Pretest-posttest design : use of this does not necessarily mean your experiment is a quasi- experiment but you can use this for a true experiment as well. M1 Treatment M2 M1 No treatment M2 But you randomly assign the subjects to both groups (EXPERIMENT) One group pretest-posttest design M1 Treatment M2, M2>M1 but you want to know that this was caused by the treatment ONLY. However, you cannot conclude this because it is subject to all the threats : 1. History 2. Maturation 3. Testing 4. Instrument decay M1 Treatment M2 non-equivalent control group pretest-posttest M1 No Treatment M2 you are using preformed groups for both and because we did not randomly assign subjects to both groups, we cannot assume that they are equivalent. However, it can rule out alternative explanations based on the threats. If M2>M1, we can rule out history because of the non-equivalent control group because if something out in the real world was actually making them better at time of M2 than M1, then the non-equivalent control group would be affected too. Even though they are non-equivalent groups, any extra differences between M2 and M1 in the first group can be attributed to our treatment because any differences caused by the threats will be evident in both groups. However, this adds another threat:
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This note was uploaded on 03/07/2011 for the course PSYCH 100B taught by Professor Staff during the Fall '01 term at UCLA.

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Lecture 8 11.23.09 - 11/23/09 Psych 100B Lecture 8 Using...

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