Scatter Plot

Summary
x = explanatory

y = response

1) direction: positive/negative association (slope)

2) form: straight/linear or curved (gently/sharply)

3) strength: small/large amount of scatter

4) unusual/unexpected values: outliers, gaps

Correlation Coefficient (r)
r = slope of the line that best fits the z-scores (zx,zy)

r measures the strength of the linear relationship between 2 sets of quantitative data

Conditions to use correlation coefficient
1) quantitative variable condition

2) straight enough condition

3) outlier condition

Correlation
1) sign gives direction

2) always between -1 and 1

3) correlation x w/y = y w/x

4) no units (z-scores have no units)

5) not affected by changes in center, scale, or units