Presentation on theme: "CHAPTER 38 Scatter Graphs. Correlation To see if there is a relationship between two sets of data we plot a SCATTER GRAPH. If there is some sort of relationship."— Presentation transcript:
Correlation To see if there is a relationship between two sets of data we plot a SCATTER GRAPH. If there is some sort of relationship between the two variables we call this relationship CORRELATION. If there is CORRELATION the points of the SCATTER GRAPH will lie almost on a STRAIGHT LINE. If both variables increase together this is called POSITIVE CORRELATION eg a person’s height and their shoe size. If one variable decreases as the other variable increases this is called NEGATIVE CORRELATION eg a car’s value and its age. If the points are very close to a straight line the CORRELATION is STRONG. If no pattern is spotted in the variables there is ZERO CORRELATION.
Line of Best Fit If there is STRONG CORRELATION between the two variables it is possible to draw a LINE OF BEST FIT on the SCATTER GRAPH. The LINE OF BEST FIT is drawn so that there is the same number of points above and below the line. The SLOPE of the LINE OF BEST FIT shows the trend of the points. The LINE OF BEST FIT does not have to go through the origin of the graph. The LINE OF BEST FIT can be used to take readings from the SCATTER GRAPH.