Communications 88 Lecture 11-12

Communications 88 Lecture 11-12 - Communications 88 Lecture...

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Communications 88 Lecture 11-12 Threats to Internal Validity Selection Bias o If you randomly assign groups then there is no selection bias History Effect o Could be a huge event or a small thing, 2 two schools, 1 gets suicide awareness and other doesn’t, and that 1 is more aware, but you don’t know if that school had a recent suicide Statistical Regression (to the mean) o If you start out with a extreme score chance alone is that the next time the score will go down a little bit, o Threat because if you choose people with extreme scores then the manipulation probably didn’t affect them but by the chance alone, Contamination (of conditions) o Send blood work to a lab and then that blood gets contaminated, o Mood manipulation test, happy and sad, so the people watching the happy movie can hear something sad in the other room, then that affects them o Or if you tell someone they will be watching “porn” and they get in there and they don’t watch porn, then they will know they are in the control group and that affects
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This note was uploaded on 01/25/2011 for the course COMM 88 taught by Professor Jansma during the Spring '08 term at UCSB.

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Communications 88 Lecture 11-12 - Communications 88 Lecture...

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