Midterm Lecture 6c Flashcards
Correlation
A linear relationship is said to be strong if the points in the scatter plot lie closely to the line and weak if they are widely scattered about the line
-we need a statistical test to fit the line to the points on the scatter plot.
Scatter Plot
displays the direction, form, and strength of the relationship between two variables.
outliers
aka extreme scores
correlation scale
A correlation measures the strength and direction of the linear relationship between two variables
-denoted by letter r
-vales will range between -1.00 and +1.00
-the closer the value is of r (negative or positive), the stronger the relationship
Correlation -1.00
Negative relationship or inverse relationship
-for every unit of increase in one variable, there is one unit of decrease in the other variable
-line angled downwards
Correlation 0.00
Indicates there is no relationship between the variables
(points are all scattered)
Correlation +1.00
-positive relationship
-for every unit of increase in one variable there is one unit of increase in the other
-line angled upwards
Correlation Calculation
Step 1: list all scores for the first variable (X)
Step 2: sum all the scores for X, EX
Step 3: square each of the scores for X, X^2
Step 4: sum all the squared values of X, EX^2
Step 5: list all scores for second variable (Y)
Step 6: sum all the scores for Y, EY
Step 7: square each of the scores for Y, Y^2
Step 8: sum all the squared values of Y, EY^2
Step 9: multiply each score for X by Each corresponding score for Y. EXY
Step 10: insert all values into formula
r= nEXY-(EX)(EY) / square root [nEX2-(EX)2] [nEY2-(EY)2]
Relationship Status
0.90 to 1.00-Very strong correlation
0.70 to 0.89-strong correlation
0.40 to 0.69-moderate correlation
0.10 to 0.39-Weak correlation
0.00 to 0.09-Negligible correlation
