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 # Correlation
 ## Scatter Diagrams
 A scatter diagram or scatter plot shows the relationship between two variables. One variable is on the X axis, the other on the Y axis. 
+
+If a scatter diagram is football shaped, it can be summarized using the 5-number summary:
+
+| Variable | Description |
+| -- | -- |
+| $ave_x$ | |
+| $SD_x$| |
+| $ave_y$ | 
+| $SD_y$ | |
+| $r$ | | 
+
+
+
 ### Association
-- Positive association is demonstrated when the dots are trend upward as $x$ increases. 
-- Negative association is demonstrated when the the dots trend downward as $x$ increases.
-- Strong association is demonstrated when dots are clustered tightly together along a line.
-- Weak association is demonstrated when dots are not clustered tightly. 
+- Positive association is demonstrated when the dots are trend upward as $x$ increases ($r$ is positive). 
+- Negative association is demonstrated when the the dots trend downward as $x$ increases ($r$ is negative).
+- Strong association is demonstrated when dots are clustered tightly together along a line ($|r|$ is closer to 1).
+- Weak association is demonstrated when dots are not clustered tightly.  ($|r|$ is closer to 0)
 ## Correlation
 Correlation is between `-1` and `1`. Correlation near 1 means tight clustering, and correlation near 0 means loose clustering.  $r$ is -1 if the points are on a line with negative slope, $r$ is positive 1 if the points are on a line with a positive slope. As $|r|$ gets closer to 1, the line points cluster more tightly around a line.