Part II: Descriptive Statistics Chapter 7 Plotting Points and Lines

1
Part II Descriptive StatisticsChapter 7
Plotting Points and Lines
2
Chapter 7 Slope
Take any 2 points (A and B) on a line
Moving from A to B
X changes in some way
Y changes in some way
B
Rise 1
A
Run 2
Ratio of rise slope run Slope the rate
at which y changes for each unit change in x
how much does y change as x changes one unit Here
the slope 1/2 0.5
3
Positive, Negative, 0 Slope Values
0 change in y 0 slope
change in y slope
- change in y - slope
4
Intercept
the height of the line where the line crosses the
Y axis
Intercept 0.50
Intercept 4
Intercept -3
5
Plotting Lines
Plot the line passing through the point (1, 1)
with a slope of 2/3
Construction point
Run 4
Rise 2.7
The next step involves the slope
slope rise/run which here 2/3 we chose the
run 4 the rise should be positive (it is not
-2/3) Rise slope x run 2/3 times 4 2.7
6
Plotting Lines
Plot the line passing through the point (1, 1)
with a slope of 2/3
Construction point
Run 4
The next step involves the slope
slope rise/run which here 2/3 we chose the
run 4 the rise should be positive (it is not
-2/3) Rise slope x run 2/3 times 4 2.7
7
Algebraic Equation for a line
rule for computing the y coordinate of a point
from its x coordinate
y 0.25x 2 OR y 2 0.25x
intercept
x coordinate
General form y mx b
slope
8
Algebraic equation for a line of the rule y
.25x 2
x 4 8 12 16
y .25x 2 .25(4) 2 .25(8) 2 .25(12)
2 .25(16) 2
y 3 4 5 6
Rise 2
Run8
Note slope rise/run 2/8 1/4 0.25 all
points fall on the line line the graph of the
equation
the graph of the equation y mx b is a
straight line with slope m and interce
pt b
9
Algebraic equation for a line of the rule y
-.75x 4
x 0 2 4 6
y -.75x 2 -.75(0) 4 -.75(2) 4 -.75(4)
4 -.75(6) 4
y 4 2.5 1 -0.5
Run 2
Rise -1.5
Note slope rise/run -1.5/2 -3/4
-0.75 all points fall on the line
the graph of the equation y mx b is a
straight line with slope m and interce
pt b