PM511A - Midterm Week 3

slope interpretation format for:

log (y)
X = x centered on its mean

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slope interpretation format for:

log (y)
X = x centered on its mean

A 1 unit increase in X is associated with a 100(e^B-1) percent increase in Y

intercept interpretation format for:

log (y)
X = x centered on its mean

The geometric mean of Y is e^B unit at the average X.

interpret the intercept for the following reg (meaningful and not):

y = log distance
x = MPH_MPHbar

intercept = 4.4
slope = 0.06492

- The mean log stopping distance is 4.40 log feet at the average speed.

- The geometric mean stopping distance is exp(4.4)=81.52 feet at the average speed.

interpret the slope for the following reg (meaningful and not):

y = log distance
x = MPH_MPHbar

intercept = 4.4
slope = 0.06492

A 1 MPH increase in speed is associated with a 0.065 log feet increase in the average stopping distance.

A 1 MPH increase in speed is associated with a 6.7% increase in stopping distance.

What is Pearson's correlation coefficient used for?

R measures STRENGTH and DIRECTION of the linear relationship between two continuous variables

R = 1 (Pearson's correlation)

perfect positive linear relationship

R = 0 (Pearson's correlation)

no linear relationship

R = -1 (Pearson's correlation)

perfect negative linear relationship

tools for exploratory data analysis EDA?

- proc print: look at data

-proc univariate: examine distributions

- proc sgplot: scatter of variables

proc corr (simple)

proc corr data = A;
var chol tg bmi;
title 'Calculate pairwise correlations of chol, tg, & bmi';
run;