First sketch a line that closely fits the data. Second, locate two points on the line. They don't have to be one of the original data points. We, will choose, (4,60) and (7,80) for this example. Now find the equation of a line using the previous learned techniques.
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m = (80-60) / (7-4)
m = 20 / 3
m = 20/3
y = mx + b
y = 20/3x + b
60 = (20/3)4 + b
60 = 80/3 + b
100/3 = b
Thus a best fit equation is:
y = 20/3x + 100/3
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A scatter plot shows the relationship between 2 variables. We will look at three relationships between x & y: Positive, Negative and No relationship.
 
The Internet project under 'Assess' on the bar at the left is a performance assessment using presidential election data to make a scatter plot, best fit line and predictions about future trends.
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