# Session__11 - Introduction to Correlation A scatterplot is...

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Introduction to Correlation

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A scatterplot is a graphical way to visualize the relationship between two variables. From http://www.mzandee.net/~zandee/statistiek/stat- online/chapter4/pearson.html
A correlation is statistical technique used to measure and describe a relationship between two variables. In a large sample, the correlation between wife’s age and husband’s age was r = 0.97.

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Relationships between variables can be characterized in three ways: 1. Direction of the relationship 2. Form of the relationship 3. Degree of the relationship
Correlations can be classified as either positive or negative. In a positive correlation, the variables tend to move in the same direction. As X increases, Y also increases. In a negative correlation, the variables tend to move in the opposite direction. As X increases, Y decreases. r = +1.0 r = -1.0

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The sign of the correlation will indicate the direction of a relationship r = +1.0 r = -1.0 Positive correlation Negative correlation
The form of the relationship concerns the shape formed in the scatterplot. The most common use of correlation is to measure straight-line relationships. Other types of correlations exist, such as curvilinear, U-shaped, or S-shaped. We’ll be focusing on linear relationships.

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the data fits the form being considered. For example, how well does the data fit a straight line? Data that fits a straight
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## This note was uploaded on 01/27/2011 for the course EDPSY 400 at Pennsylvania State University, University Park.

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Session__11 - Introduction to Correlation A scatterplot is...

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