STAT 1301 Chapter 8 Scatter Plots, Correlation
For Regression Unit You Should Know n How to plot points n Equation of a line Y = mX + b m = slope b = Y-intercept n Plotting line from equation Y = 3X + 2
Data Set X Y Y X
Y X X Y X Y Y = 3X + 2 Y = 3X + 2..
For Regression Unit You Should Know n How to plot points n Equation of a line Y = mX + b m = slope b = Y-intercept n Plotting line from equation Y = 3X + 2 n Chapter 7 - Good Review if needed
Histogram n displays distribution of 1 variable Scatter Diagram Scatter Diagram n displays joint distribution of 2 variables n plots data as “points” in the“x-y plane.”
Association Between Two Variables indicates that knowing one helps in predicting the otherindicates that knowing one helps in predicting the other n Linear Association our interest in this courseour interest in this course points “swarm” about a linepoints “swarm” about a line n Correlation Analysis measures the strength of linear associationmeasures the strength of linear association
Hypothetical Father-Son Data
(association)
Regression Analysis n we want to predict the dependent variable using the independent variable DependentVariable(Y) Independent Variable (X)
Correlation Coefficient - measures linear association perfect no perfect perfect no perfect negative linear positive relationship relationship relationship n We use the letter “ r ” to denote the correlation coefficient.
Positive Correlation - - high values of one variable are associated with high values of the other Examples: n Father’s height, son’s height n daily grade, final grade n r = 0.93 for plot on the left
Negative Correlation - - high with low, low with high Examples: n Car weight, miles per gallon n Days absent, final grade n r = for plot shown here
Zero Correlation - - no linear relationship Examples: n height, IQ score n r = 0.0 for plot here
-.75, 0,.5,.99
r = 0.00
r = 0.40
r =
r = 0.8
r = 0.95