1.7 Correlation

Do ‘Opening Problem’ p. 572

Correlation – the relationship between two variables

Positive Correlation – as one variable increases, the other variable increases.

Negative Correlation - as one variable increases, the other variable decreases.

For both of these, the spread of the dots on the scatter plot represents another characteristic of a correlation-the strength. Correlations can also be characterized strong, moderate, or weak. Next lesson we will be classifying these mathematically. For now, eyeball it.

You may need to discuss whether or not the scatter plot has a linear or non-linear pattern.

Outliers are points that are significantly removed from the pattern of points considering where the pattern goes.

Causation

When discussing a correlation, the end result is looking for some sort of causal relationship between the variables. Global Warming is an example of a (debated) causal relationship between CO2 emissions and temperature. The correlation is not the whole story, sometimes correlations don’t imply causality.

For example: more women are entering into engineering programs in the past 5 years and more reality tv shows are being shown on tv in the past 5 years. Therefore, the number of reality shows on tv is dependent on the number of women in engineering.

This is an accidental causal relationship.

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