BIOL-337 Lecture Notes - Lecture 2: Frequency Distribution, Categorical Variable, Quartile
16 Jan 2018
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Lecture 2: graphics: displaying data: data, variables & distributions, data & variable types. Data: measurements of one or more variables made on a sample of individuals. Variable: any characteristic/measurement on individuals drawn from a population under study. Categorical variables: class (membership, nominal (name) or ordinal (order) Some caveats: discrete numerical variables often analysized as continuous: if large # possible values, variable indexed by number does(cid:374)(cid:859)t (cid:373)ea(cid:374) its (cid:374)u(cid:373)eri(cid:272)al, may just name a category, numerical data may be reduced to categorical data by grouping. Interval: equal distance from each other, measured along the continuum, degrees celsius, degrees fahrenheit, ratio. Interval, but 0 truly means nothing: height, mass, distance, ratio of measurement. Possibly the 1st and the most important distinction. Types of studies: experimental study, researcher assigns treatments randomly, e. g. : clinical trial: cause and effect, tough and expensive, observational study, assignment of treatments not made by researcher, e. g. : effects of smoking: only point to associations, displaying data, frequency distributions.
