1.9 Graphing Data on the Coordinate Plane Two number lines that intersect at right angles form a coordinate plane. X- axis – the horizontal axis Y- axis – the vertical axis Origin – where the axes intersect (0, 0) Quadrants – the four sections of the coordinate plane.

Coordinate Plane y - axis x - axis Origin (0, 0) ( +, +)( -, +) ( -, -) ( +, -)

Graphing Points An ordered pair of numbers identifies the location of a point. These numbers are the coordinates of the point on the graph. (x-coordinate, y-coordinate) (-2, 4)

Identifying Coordinates ZT W O Q V P

Identifying Coordinates Name the coordinates of each point on the graph. Point O Point P Point Q Point T Point V Point W Point Z (0, 0) - origin (-4, 1) (0, 2) (3, -3) (-1, 1) (4, 1) (-2, -3)

Graphing Points Graph the point A (3, -4) on the coordinate plane. A

Identifying Quadrants In which quadrant or on which axis would you find each point. a.(-1, 5) Since the x-coordinate is negative, and the y-coordinate is positive, the point is in Quadrant II. b. (0, 3) Since the x-coordinate is 0, the point is on the y-axis.

1.9 Graphing Data on the Coordinate Plane (Cont.) 9/29/10 A scatter plot – a graph that relates two groups of data. –Most scatter plots are in the first quadrant of a coordinate plane, because the data are usually positive numbers.

Scatter Plot Year Number of Households With Television (millions)

Scatter Plots Positive correlation – in general, both sets of data increase together. Negative correlation – in general, one set of data decreases as the other set increases. No correlation – sometimes data sets are not related. Trend line – shows a correlation more clearly Positive Correlation Negative Correlation No Correlation