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# Section 3.1 Scatterplots and Correlation

AP Statistics
by

## Armando Murillo

on 1 October 2014

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#### Transcript of Section 3.1 Scatterplots and Correlation

Describing Relationships
Explanatory vs Response Variables

Response measures an outcome of a study
Explanatory variables help explain or influence changes in a response variable

Interpreting Scatterplots
Direction (positive, negative, neither)
Form (linear, curved, neither)
Strength (strong, moderately strong, weak, really weak, really really weak)
Outliers
Measuring Linear Association: Correlation
Correlation r: measures the direction and strength of the linear relationship between two quantitative variables
Properties of r
r is always a number between -1 and 1

r > 0 indicates a positive correlation

r < 0 indicates a negative correlation

r values near 0 indicate a very weak linear relationship

strenght of the relationship increases as r moves away from 0 towards -1 or 1
Scatterplots
shows the relationship between two quantitative variables measured on the same individual
Section 3.1 Scatterplots and Correlation
Explanatory or Response ?
weed growth and rain
basketball team's winning percentage and attendance
amt of daily exercise and resting pulse rate
How to make a Scatterplot
1. Decide which variable should go on each axis (Always plot the eXplanatory variable on the x-axis)

2. Label and scale your Axes

3. Plot individual data values
correlation Practice
Ap Statistics Mr. Murillo
Full transcript