The points for Person 1 and Person 6 are both above the line. Why is the point for Person 1 farther away from the line?
Person 1 has an arm span of 156 cm and a height of 162 cm, which is the coordinate point (156, 162) in the scatter plot. A hypothetical person represented by the coordinate point (156, 156) would be on the line Height = Arm Span, as shown below:
The vertical distance from a point to the line is the absolute value of the difference in y-coordinates from the first point and the point on the line directly above (or below) that point. In this case, Person 1's point (156, 162) is six above the line's point (156, 156). Therefore, the vertical distance from Person 1's point to the line is 6.
Put another way, the vertical distance from (156,162) to the line Height = Arm Span is the magnitude (or absolute value) of the difference between the height and the arm span.
The vertical distance is: |Height - Arm Span| = |162 - 156| = |6| = 6.
In a similar way, the vertical distance from the point for Person 6 (which is [161,162]) to the line Height = Arm Span is: |Height - Arm Span| = |162 - 161| = |1| = 1.