Unit D: Graphing

Summary

A scatterplot is used to determine if there is a relationship or connection between two sets of data (the dependent variable and the independent variable)

A positive correlation (positive linear trend) occurs when the scatterplot appears to form a line that rises from left to right (as the x-values increase, the y-values increase).
A negative correlation (negative linear trend) occurs when the scatterplot appears to form a line that falls from left to right (as the x-values increases, the y-values decrease).
If the points on the scatterplot seem to be scattered randomly, there is no trend, or no correlation, between the variables.

The line of best fit (or "trend" line) is a straight line that best represents the data on a scatterplot. In can display positive correlation or negative correlation.
The line of best fit must be drawn with a straight edge.
An outlier is a data point that lies significantly outside the general trend of the data. When drawing the line of best fit, outliers can be disregarded if it is evident that those one or two points do not follow the trend.
In the case of no correlation, no relationship exists between the two variables, so the line of best fit cannot be drawn.
The line of best fit is useful to estimate values on a scatterplot using interpolation or extrapolation.