- As in any graph of data, look for the overall pattern and for striking deviations from that pattern
- You can describe the overall pattern of a scatterplot by the direction, form and strength of the relationship
- An important kind of deviation is an outlier, an individual value that falls outside the overall pattern of the relationship
Positive Associations: Two variables are positively associated when above-average values of one tend to accompany above-average values of the other and below-average values also tend to occur together. The scatterplot slopes upward as we move from left to right.
Negative Associations: Two variables are negatively associated when above-average values of one tend to accompany below-average values of the other, and vice versa. The scatterplot slopes downward from left to right.
Correlation: correlation describes the direction and strength of a straight-line relationship between two quantitative variables. Correlation is usually written as "r". "r" is the correlation coefficient, it measures how strong the correlation is.
- A measure of how closely associated two variables are. it's measured between -1 and 1.
- Zero means no association
- -1 means a perfect negative linear association
- 1 means a perfect positive linear association