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

Z T

W

O

Q

VP

Identifying CoordinatesName 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

Media in the United States

050

100150

1900

1950

2000

2050

Year

Num

ber

of

Household

s w

ith

Tele

vis

ion

Series1

YearNumber of Households With Television

(millions)

1950 4

1960 46

1970 59

1980 76

1990 92

2000 101

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