Scatter Diagrams And Correlation (4) Flashcards
What is association
Two variables with a relationship between them
What data do scatter diagrams show
Bivariate data
Where do you plot the independent variable
On the horizontal x axis
What does the independent variable show
It shows the value you change
Where do you plot the dependent variable
On the y axis
What does the dependent variable show
The value you do not change
It depends on the explanatory variable
What is correlation
The link between two variables that shows a trend
What is positive correlation
When one variable increases another increases
What is negative correlation
When one increases the other decreases
What is linear correlation
When they lie on a straight line
(This can be positive or negative)
What is non linear correlation
Correlation that shows a curved line
What is a causal relationship
When a change in one variable directly causes a change in another variable.
E.g. The larger a fuel tank the more fuel a car uses
Does correlation directly imply causation
No
Correlation doesn’t always mean there is a causal relationship.
How many factors will cause a change in variables
Multiple.
Although a single scatter graph will show how one factor effects another there may be multiple
What is a line of best fit
A straight line drawn so the plotted points on a scatter diagram are evenly scattered either side of the line
