HSS 2381 Lecture 9: Correlation and Regression
30 Nov 2016
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Hss2381 lecture 9 - correlation and regression. What is a math/stats model: often describe relationship between variables, types, deterministic models (no randomness, probabilistic models (with randomness) Deterministic models: hypothesize exact relationships, suitable when prediction error is negligible, example: body mass index (bmi) is measure of body fat based, metric formula, non-metric formula. 1- hypothesize 2 components: deterministic, random error. 2- example: systolic blood pressure of newborns is 6 times the age in days + random error: sbp = 6xage(d, random error may be due to factors other than age in days (e. g. birthweight) Regression" provides a functional relationship (y=f(x)) between the variables; the function represents the average relationship. Correlation tells us the direction and the strength of the relationship. The analysis starts with a scatter plot of y vs x. A descriptive index that summarizes magnitude and nature (direction) of a relationship between two variables in a sample. Can also be used to make inferences about relationships in the population.
