# The Correlation Coefficient

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1. Who created the Product-Moment Correlation Coefficient?
Karl Pearson
2. What is the correlation coefficient?
• A model dependent measure of the strength of relationship between two variables
• It provides an appropriate measure of the strength of a relationship only within the context of linear regression
3. What happens if the relationship between variables is non linear?
The use of the correlation as a descriptive statistic is misleading
4. What does the interpretation of the coefficient assume?
• An underlying bivariate normal distribution
• Normally distributed condition distributions
• Homogeneity of variance
5. What are the relationship denotations for the correlation coefficient?
• When there is a perfect positive linear
• relationship, r = 1.0

• When there is perfect negative linear
• relationship, r = -1.0

• When r = 0.0 there is either no relationship,
• (or possibly a non-linear relationship)
6. What is the probability formula for the coeffient?
• The square root of r2
• If the regression coefficient is negative the r value should also be made negative
• This means the correlation coefficient is the square root of the proportion of variability accounted for by the straight line regression
7. What must be remembered when using R2?
• R2 must be expressed as a proportion when taking the square root (not a percentage)
• r varies between -1.0+1.0 whereas R2 varies between 0.0+1.0
8. Give a formula to relate the correlation coefficient to the regression coefficient
r= slope x the square root of the sum of squares of x over the sum of squares of y
9. What happens if X and Y are converted into standard scores (M=0.00, SD=1.0)
• The value of the coefficient will not be affected
• The SD will be the same for both
 Author: camturnbull ID: 297183 Card Set: The Correlation Coefficient Updated: 2015-03-01 15:24:20 Tags: Stats Folders: Stats Description: . Show Answers: