Chapter 5 Flashcards
What is correlation?
A measure of the strength of the linear association between two variables
What is a negative correlation?
When one variable decreases as the other increases
What is a positive correlation?
When one variable increases as the other increases
What does association not necessarily mean?
There is a linear correlation
When a change in one variable directly causes a change in another variable, what is there?
A causal relationship
What does correlation not necessarily imply?
A causal relationship
When points on a scatter diagram are strongly correlated along a straight line what are they?
Strongly correlated
What is a line of best fit?
A straight line drawn so that the plotted points on a scatter diagram are evenly scattered either side of the line.
A line of best fit is a model for the association between two variables.
A line of best fit should pass through the mean point
If the points on a scatter diagram lie approximately on a straight line, there is a linear relationship between them. What does this mean?
They are associated
What is interpolation?
When the data point you need lies within the range of the given values
What is extrapolation?
When the data point you need lies outside the range of given values
What is the equation if the line?
y = ax + b
The a is the gradient and the b is the y-intercept
Remember for the gradient rise over run/ height ➗ by base
For y-intercept, rearrange the equation with coordinates
Go page 206
And look at the linear models
What is spearman’s rank correlation coefficient?
It is a numerical measure of the correlation between two sets of data. It tells us how close the agreement is.
d if the difference and n is the number of observations
In spearman’s rank, if the answer is close to 1 what is there?
A strong positive linear correlation
