1. Scientific Inquiry SCI 105.020 Correlation Vs. Causation

2. Correlation Correlation is a relationship between two variables, each with various numbers of possible values. Variables Color Size Values Red, Green Large, Small

3. Correlated or Not Not correlated Correlated Small Large Red Green Small Large Red Green

4. Causation Correlation is a necessary condition for a causal relationship, but not a sufficient one Examples  Using ashtray & suffering lung cancer  Red spots, fever and measles C Cause Not C E Effect Not E

5. Causation Is Not Symmetric Correlation is symmetric  Being small is negatively correlated with being red.  Being red is also negatively correlated with being small. Causation is not  Smoking causes cancer  Suffering cancer causes smoking (???) Small Large Red Green CE

6. Find out the Hidden Variable In many situations, two correlated variables are not linked with a casual relationship directly. But there is a hidden variable that determines the association.  Using ashtray   lung cancer  Hidden variablesmoking

7. Sample Data Day MinutesDay CallsDay Charge 265.111045.07 161.612327.47 243.411441.38 299.47150.9 166.711328.34 223.49837.98 218.28837.09 1577926.69 184.59731.37 258.68443.96 129.113721.95 187.712731.91 128.89621.9 156.68826.62 120.77020.52 332.96756.59 196.413933.39 190.711432.42

8. Scatter Plot – No-Association

9. Scatter Plot - Strong Association

10. Scatter Plot – Linear-Linear

11. Scatter Plot – Linear-Logarithmic