# IPS6eCh02_2bb - Looking at Data Relationships Correlation...

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Looking at Data - Relationships   Correlation IPS Chapter 2.2

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Objectives (IPS Chapter 2.2) Correlation The correlation coefficient “r” r does not distinguish between x and y r has no units of measurement r ranges from -1 to +1 Influential points
The correlation coefficient "r" The correlation coefficient is a measure of the direction and strength of a linear relationship. It is calculated using the mean and the standard deviation of both the x and y variables. Correlation can only be used to describe quantitative variables. Categorical variables don’t have means and standard deviations.

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The correlation coefficient "r" Time to swim: x = 35, s x = 0.7 Pulse rate: y = 140 s y = 9.5
Part of the calculation involves finding z, the standardized score we used when working with the normal distribution. You DON'T want to do this by hand. Make sure you learn how to use your calculator or software.

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Standardization: Allows us to compare correlations between data
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