lecture 8 correlation1

lecture 8 correlation1 - Correlation Two variables are...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Correlation Two variables are correlated if knowing something about one tells you something about the other Height and Weight (+) Heavy smoking and Life expectancy (-) Height and Life expectancy (uncorrelated) Age and Strength (curvilinear) 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Linear Correlation: Pearson’s r A measure of the strength, and direction, of the linear relationship between two variables Takes values ranging from 1 to -1 Values of r close to 1 or -1 indicate a stronger relationship; values close to 0 indicate a weaker relationship Positive values indicate a positive relationship; negative values indicate a negative relationship 2
Background image of page 2
z Score formula for r r = z x z y n - 1 Where z x and z y are the sample z -transformed scores for the i th individual on the variables x and y , and n = the number of paired observations in the sample (i.e., half the total number of scores) z x = z x = x i - X s x y i - Y s y 3
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Covariance Var(x) =E(x - µ ) 2 =E(x - µ )(x - µ ) = Cov(x, x) Cov(x, y) =E(x - µ x )(y - µ y ) = (x - µ x )(y - µ y ) N Where N = the number of paired observations in the population data set {X,Y} 4
Background image of page 4
Covariance Positive values of Cov(x, y) indicate that higher values of
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/21/2009 for the course PSYC 60 taught by Professor Ard during the Winter '08 term at UCSD.

Page1 / 19

lecture 8 correlation1 - Correlation Two variables are...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online