Comparing Two Continuous Variables - Duke University

Comparing Two Continuous Variables

STA 102: Introduction to Biostatistics

Sam Berchuck

April 1, 2021

STA 102: Introduction to Biostatistics

Sam Berchuck

Lecture 16 Slide 1

Department of Statistical Science, Duke University

Very Optional Readings

I P&G: Chapter 17

I OI: Section 8.1

STA 102: Introduction to Biostatistics

Sam Berchuck

Lecture 16 Slide 2

Department of Statistical Science, Duke University

Motivation

Comparisons of interest:

I Categorical predictor vs. categorical outcome (Fisher¡¯s exact

test or ¦Ö2 test)

I Categorical predictor vs. continuous outcome (t-tests,

ANOVA, and their non-parametric alternatives)

I Continuous predictor and continuous outcome (will begin

discussion today!)

I Continuous predictor and categorical outcome (will discuss

April 13)

I ...even more exotic types of comparisons (April 15)

STA 102: Introduction to Biostatistics

Sam Berchuck

Lecture 16 Slide 3

Department of Statistical Science, Duke University

Remember this plot?

Aerobic Activity vs. Obesity, US States

Obesity (%)

35

30

25

40

45

50

55

60

65

Adequate aerobic activity (%)

STA 102: Introduction to Biostatistics

Sam Berchuck

Lecture 16 Slide 4

Department of Statistical Science, Duke University

Remember this plot?

Aerobic Activity vs. Obesity, US States

Obesity (%)

35

30

25

40

45

50

55

60

65

Adequate aerobic activity (%)

Some questions of interest may include:

I Direction of relationship: are the variables positively or

negatively related?

I Form: is any relationship linear or more complex?

I Strength of relationship: how accurately can one variable

predict the other?

I Influential points: are one or a few points driving the

relationship we see?

STA 102: Introduction to Biostatistics

Sam Berchuck

Lecture 16 Slide 5

Department of Statistical Science, Duke University

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