Note last two course objectives from text page 19:
3. Define and calculate the slope of a line.
4. Graph relationships among more than two variables.
3. Outline
III. The Slope of a Relationship
A. The slope of a curve equals the change in the
value of the variable on the vertical axis at the point(s) where the slope is being
calculated divided by the change in the value of the variable on the horizontal axis at
the relevant point(s).
1. In terms of symbols, the slope equals Dy/Dx,
with D standing for "change in."
B. The slope of a straight line is constant. The slope
is positive if the variables are positively related and negative if the variables are
negatively related.
C. The slope of a curved line at a pointequals
the slope of the straight line that is tangent to the curved line at the point.
D. The slope of a curved line across an arc equals the
slope of the straight line between the two points on the curved line.
IV. Graphing Relationships Among More Than Two
Variables
A. When a relationship involves more than two variables,
diagrams showing the relationship between two of the variables hold all other pertinent
variables constant.
1. Holding other variables constant uses the idea of ceteris
paribus, which is the Latin expression for "other things remaining the
same."
2. When one of the other variables not graphed changes, the
entire graphed relationship shifts to another curve.
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6. Homework
1. Review Helpful Hints in your study guide
on pages 12 -13.
2. Complete even-numbered Questions in your study guide
pages 13 -18 and check your answers in study guide pages 19 - 23.
3. If not done in class, complete the Two-Minute-Feedback.
4. Visit and register at www.Econ100.com as a member. Take a look at the
Learning Tools. Within Learning Tools you can:
Take a quiz;
Engage in RBL;
Get study help;
Connect with economic links.
7.
Summary
Direct or positive relationships between
two variables can be seen at a glance at a graph of two variables.
Inverse or negative relationships between
two variables can be seen at a glance at a graph of two variables.
Maximum and minimum values of variables
can be seen at a glance at a graph of two variables.
Variables that are unrelated can be
instantly recognized as horizontal or vertical lines when graphs of two variables show
such relations between each other.
Using the methods mentioned on daily class
outline, you can find the slope of a curved line (as the slope of its tangent) and the
slope of an arc (as the slope of the line connecting the two points on the arc).
Ceteris Paribus is an important principle allowing models to discover relationships
between any two variables, so long as the size or magnitude of all other variables
affecting the relation are held constant.
8.
Preview
The next chapter introduces the dominant
facts which govern our lives:
We have limited resources.
We have unlimited wants.
The primary resources are of four kinds.
Having to make choices about their wise use is another inescapable fact of life.
The consequence of having to choose how
resources are used produces (within the case of two possible uses) a Production
Possibility Frontier (PPF).
Within the context of the PPF, you'll
discover what it means to:
Use resources efficiently;
How an economic system leads to economic
growth;
How two countries, states, cities,
industries, or persons can improve their production and consumption.
9.
Two Minute Feedback
Take a minute and jot down the problem,
idea, or concept that was most interesting to you from this chapter.
Take another minute and jot down the
problem, idea, or concept with which you struggled the most.
