3.2 Correlation Pg. 140-147

Correlation Measures the direction and strength of the linear relationship between two quantitative variables. Usually written as r.

The correlation coefficient r Is defined as: 𝑟= 1 𝑛−1 𝑥 𝑖 − 𝑥 𝑠 𝑥 𝑦 𝑖 − 𝑦 𝑠 𝑦 Where we have data on variables x and y for n individuals. See pg. 142-143 #3.24

How to interpret correlation…pg. 143-144 Correlation makes no distinction between explanatory and response variables. Doesn’t matter what you call x or y when calculating correlation. Correlation requires both variables be quantitative. Because r uses standardized values, r does not change when we change units of measurement of x, y, or both. r itself has no unit of measurement, it is just a number. Positive r indicates positive association and negative r indicates negative association

Interpretation continued Correlation r is always a number between -1 and 1. values near 0 indicate a very weak linear relationship. Values close to -1 or 1 indicate that points in a scatterplot lie close to a straight line. Correlation measures the strength of only linear relationships Like mean and standard deviation, correlation is not resistant. r is strongly affected by outlying observations.

Complete the following problems Starting on page 129: Assignment Read pg. 140-145 Complete the following problems Starting on page 129: #3.10, 3.11, 3.12, 3.15, 3.25, 3.30