L4 Scatterplots - Part 2
Completion requirements
Unit D: Graphing
If the points on the scatterplot appear to form a line that rises from left to right (as the x-values increase, the y-values increase), there is a positive linear trend, or positive correlation, between the variables. When comparing the amount of time spent on homework with the test mark, it can be seen that as the time spent on homework increases, the test mark increases. Graph A shows positive correlation.
If the points on the scatterplot seem to form a line that falls from left to right (as the x-values increase, the y-values decrease), there is a negative linear trend, or negative correlation, between the variables. When comparing the price of the apples to the number of apples sold, it can be seen that as the price of the apples increases, the number of apples sold decreases. Graph B shows negative correlation.
Relationships between variables can be strong or weak. When the ordered pairs on a graph are close together, the correlation is strong. When the ordered pairs on a graph are farther apart, the correlation is weaker.
This scatterplot shows weak positive correlation. The points are not grouped together to form the shape of a line, so the correlation is weak. Since the y-values increase as the x-values increase, the graph shows positive correlation.
This scatterplot shows strong negative correlation. The points are grouped together to form the shape of a line, so the correlation is strong. Since the y-values decrease as the x-values increase, the graph shows negative correlation.
Sometimes a scatterplot shows that there is no relationship between the two sets of data.
Graph C: Does the outside temperature affect the number of newspapers sold?
If the points on the scatterplot are scattered randomly, there is no trend, or no correlation, between the variables. In graph C, the outside temperature does not influence the number of newspapers sold. The scatterplot shows no correlation.