lecture 11- 23

lecture 11- 23 - November 23, 2004 Quasi- Experimental...

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November 23, 2004 Quasi- Experimental Designs (not true exp’s (no RA) but have good comparison groups) Pretest- posttest quasi-equivalent groups O 1 X O 2 (group 1) O 1 O 2 (group 2) Examine pre-test scores to compare groups before manipulation Try to match groups according to similar characteristics before experiment Time Series Designs Track many observations over time , before and after a manipulation Single Group interrupted time series design -One group, manipulation is observed over time; no comparison to another group -EX: how well a test book does at a school: observe monthly test scores in one school O 1 O 2 O 3 O 4 X O 5 O 6 O 7 O 8 (group 1) -Improves the “one- group pretest-posttest” -EX: Crime prevention program -Crime rates went down from January to February -Pretest-posttest design: no control group -Can’t conclude crime went down due to lack of prior knowledge; need a lot more measures of crime from other months/years (solves some threats to internal validity- testing, maturation)
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This note was uploaded on 04/10/2008 for the course AS AM 1 taught by Professor Zhao during the Fall '08 term at UCSB.

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lecture 11- 23 - November 23, 2004 Quasi- Experimental...

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