Lect.ure 8

Correlation:
The two variables X,Yare said to be correlated if a change in one variable effects a change in the other variable . This concept of correlation refers to the degree of relationship between or more variables.
Co-efficient of Correlation Karl Pearson (1867-1936) a British Biometrician, developed the coefficient of correlation to express the degree of linear relationship between two variables Correlation co-efficient between two random variables X and Y denoted by r(X,Y)
Limits for Correlation co-efficient
Correlation co-efficient lies between -1 and +1. i.e. -1 i) If r(X,Y)= 1 the variables X and Y are said to be perfectly
possitively correlated.
ii) If r(X,Y)=- 1 the variables X and Y are said to be perfectly
negatively correlated
iii) If r(X,Y)=0 the variables X and Y are said to be uncorrelated
Problem 1
Calculate the correlation co-efficient for the following heights (in inches)
of fathers(X) and their sons(Y).

X : 65 66 67 67 68 69 70 72
Y : 67 68 65 68 72 72 69 71