1101 graphs review

8/6/2019 1101 Graphs Review

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1Appendix

Using Graphs: A Review


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Copyright 2006 South-Western/Thomson Learning. All rights reserved.

Graphs Used in EconomicAnalysis

Graphs Used in EconomicAnalysis

Display large quantity of data quickly

Facilitate data interpretation and analysis

Important statistical relationships more

apparent than from written descriptions or

long lists of numbers

Display large quantity of data quickly

Facilitate data interpretation and analysis

Important statistical relationships more

apparent than from written descriptions or

long lists of numbers


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Two-Variable Diagrams

Two-Variable Diagrams

Variable = something measured by a

number

Examples: price and quantity

View two variables together to see if they

exhibit a relationship.

Variable = something measured by a

number

Examples: price and quantity

View two variables together to see if they

exhibit a relationship.


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TABLE 1: Quantities of NaturalGas Demanded at Various Prices

TABLE 1:Quantities of NaturalGas Demanded at Various Prices



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Q

b

aPPrice

Quantity(a)

140120100806040200

1

2

3

4

5

6

D

D

b

a

Q

PPrice

Quantity(b)

140120100806040200

1

2

3

4

5

6

FIGURE 1: Hypothetical DemandCurve for Gas

FIGURE 1: Hypothetical DemandCurve for Gas



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The Definition andMeasurement of Slope


Slope = ratio of vertical change to

horizontal change

Rise/run

Measure of steepness of the line

Slope = ratio of vertical change to

horizontal change

Rise/run Measure of steepness of the line


7/24Copyright 2006 South-Western/Thomson Learning. All rights reserved.



The slope of a straight line

Negative slope = one variable rises while the

other variable falls The two variables move in opposite directions.

Positive slope = two variables rise and fall

together The two variables move in thesame direction.

The slope of a straight line

Negative slope = one variable rises while the

other variable falls The two variables move in opposite directions.

Positive slope = two variables rise and fall

together The two variables move in thesame direction.


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FIGURE 2a: Negative SlopeFIGURE 2a: Negative Slope

Negative

slope

0X

Y



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FIGURE 2b: Positive SlopeFIGURE 2b: Positive Slope

Positiveslope

0X

Y



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FIGURE 2c: Zero SlopeFIGURE 2c: Zero Slope

Zero

slope

0

X

Y



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FIGURE 2d: Infinite SlopeFIGURE 2d: Infinite Slope

Infinite

slope

0X

Y



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FIGURE 3:How to Measure Slope

FIGURE 3:How to Measure Slope

310Slope =

110

Slope =

(b)(a)

A

X

B

C

1330

Y

8

11

X

AB

C

1330

Y

8

9






The slope of a curved line

Slope changes from point to point on a curved

line.Curved line bowed toward the origin has a negative

slope.

Variables change in opposite directions.

Curved line bowed away from the origin has apositive slope.

Variables change in thesame direction.


Slope changes from point to point on a curved

line.

Curved line bowed toward the origin has a negative

slope.

Variables change in opposite directions.

Curved line bowed away from the origin has apositive slope.

Variables change in thesame direction.


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FIGURE 4a:Negative Slope in Curved Lines

FIGURE 4a:Negative Slope in Curved Lines

Negativeslope

0

X

Y



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FIGURE 4b:Positive Slope in Curved Lines

FIGURE 4b:Positive Slope in Curved Lines

Positiveslope

0X

Y







A curved can have both a positive and

negative slope depending on where on thecurve is measured.

The slope at a point on a curved-line is

measured by a line tangent to that point.


A curved can have both a positive and

negative slope depending on where on thecurve is measured.

The slope at a point on a curved-line is

measured by a line tangent to that point.


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FIGURE 4c,d: Behavior of Slopein Curved Lines

FIGURE 4c,d: Behavior of Slopein Curved Lines

Negativeslope

Positiveslope

0X

Y

Negativeslope

Positiveslope

0X

Y



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FIGURE 5: How to Measure Slopeat a Point on a Curve

FIGURE 5: How to Measure Slopeat a Point on a Curve

r

r

t

t

AB

R

M

GT

E

F

D

C

Y

X109876543210

8

7

6

5

4

3

2

1




Rays Through the Origin and45-degree Lines

Rays Through the Origin and45-degree Lines

Y-intercept = point at which a line

touches they axis

Ray through the origin = straight linegraph with ay-intercept of zero

Y-intercept = point at which a line

touches they axis

Ray through the origin = straight linegraph with ay-intercept of zero


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FIGURE 6:Rays through the Origin

FIGURE 6:Rays through the Origin

12Slope = +

Slope = + 1

Slope = + 2

B

E

K

A

C

D

0

5

4

3

2

54321

1

Y

X



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Squeezing 3 Dimensionsinto 2: Contour Maps

Squeezing 3 Dimensionsinto 2: Contour Maps

Some problems involve more than two

variables

Economic contour map called aproduction indifference map

Shows how variableZchanges as we change

eitherXorY

Some problems involve more than two

variables

Economic contour map called aproduction indifference map

Shows how variableZchanges as we change

eitherXorY


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FIGURE 8:An Economic Contour Map

FIGURE 8:An Economic Contour Map

Z= 40

Z= 30

Z= 20

Z= 10

Y

ardsofCloth

per

Day

Labor Hours per Day

Y

X80706050403020100

10

20

30

40

50

60

70

80

B

A

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