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Chapter 2

PSY 2110 Chapter Notes - Chapter 2: Alf Landon, The Literary Digest, Random AssignmentPremium

2 pages88 viewsFall 2018

Department
Psychology
Course Code
PSY 2110
Professor
Marie Lyne Laliberté
Chapter
2

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Article 1: How to be a wise consumer of psychological research
All claims require evidence not just opinions
Begin with the assumption that all claims are false (innocent until proven guilty)
o Only after examining the evidence can we come to a conclusion
Decision to accept or reject a claim is best made by paying attention to the methods
that served as the basis for the claim
Two tools that lie at the heart of sound research are random sampling and
experimental manipulation based on random assignment
Random sampling
Refers to selecting people from a population so that everyone in the entire population
has an equal chance of being selected
Key to getting accurate estimate
Example: 1936 US presidential election
o Literary digest sent post cards to 10 million Americans
2 million returned
Alf Landon was the favourite
o Gallup group conducted a smaller survey with a few thousand
Franklin D. Roosevelt would be the winner
o FDR won how did Gallup poll, based on many fewer people, outperform the
Literacy Digest poll?
o Gallup poll performed a true random sample of likely voters whereas literacy
digest sampled people by taking their names from automobile registration and
telephone listings
In 1936 people who had cars and phones were wealthy and preferred Alf
Landon they had a bias sample group
Random assignment
Takes place only after people have already been selected into a study
A technique for assigning people to different specific conditions in an experiment
Random assignment only occurs when everyone in the study has an equal chance if
serving in any specific condition
In the same way that random sampling in a study will be as similar as possible to those
not sampled, random assignment guarantees that those assigned to one experimental
condition will be as similar as possible to those assigned to a different experimental
condition
Crucial because whole idea of an experiment is to be able to manipulate something
o One group gets treatment and the other doesn’t. If the group who got treatment
behaves differently we can attribute the difference to the treatment
o But only if we can guarantee the two groups were similar prior to treatment
Example: Seatbelts
o Do seatbelts save lives?
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