monfils 418_variable types

monfils 418_variable types - Sta$s$csandresearchdesign...

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Sta$s$cs and research design Lecture 4: Variables, measurement scales, validity Prof. Marie Monfils
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Stats examples?
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NYT Ar’cle: Beware of too much sleep Jerome Siegel, professor of psychiatry at the University of California, Los Angeles, and the chief of neurobiology research at the V.A. Greater Los Angeles Healthcare System. "People who sleep more than the seven‐ to eight‐ hour average have a significant reduc$on in lifespan, greater than that shown by people who sleep less than average."
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Reader comment, 6. Anon west coast Dr. Siegel clearly implies causa$on here‐‐that more sleep CAUSES shorter life span, and perhaps that's what the studies he's referring to actually show. But all he's told us is that longer sleep is CORRELATED WITH shorter life span, and there are all sorts of reasons why that could be so. There are many illnesses and condi$ons that cause weakness and fa$gue and people suffering from those oXen sleep more than 8 hours a night. So, the "shorter life span" may well be caused by condi$ons that have nothing to do with sleep per se, but that are also causing excessive sleep.This is so basic a point that it's hard to believe any reputable study could ignore it, but based on what Dr. Siegel says in this ar$cle, he seems to assume that if we sleep too much we'll get unhealthy, rather than (much more likely‐seeming) that if we're unhealthy, we'll sleep too much.
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What is a variable?
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Opera$onal defini$ons • Opera$onal defini$ons – Allow a construct to be studied – If two or more values are tested, the construct is a variable – If only a single value is used, it is a constant • e.g., Gender specific studies • Using constants limits the generality of findings • Both variables and constants can be part of an experimental design.
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