why are graphs useful? aa graph is a “picture” of your data. ggraphs can reveal patterns or...
TRANSCRIPT
CONSTRUCTING GRAPHS
Why are Graphs Useful? A graph is a “picture”
of your data. Graphs can reveal
patterns or trends that data tables cannot.
The 3 types of graphs scientists commonly use are bar graphs, circle graphs, and line graphs.
Bar Graph Used to show amounts or categories
of items.
Circle or Pie Graphs Used to show a break down of the
“pieces” that make up the “whole” of the subject graphed.
Company Expenses U.S. Energy
Consumption
Line Graphs Used to display data showing how
one variable (Responding) changes in response to another variable (Manipulated).
The voltage increases as the current increases V
olt
age
Current
CO
2
PPM
Year
Year
Tem
pera
ture
o
CGlobal Average
TemperatureAtmospheric
Carbon Dioxide Levels
Data Tables to Line Graphs
To plot a line graph follow these steps…
October Temperatures
Day Temperature o F
1 43
2 53
3 50
4 57
5 59
6 67
October TemperaturesT
emperature o F Day
1. Draw the Axes
The horizontal axis (X-axis) runs left to right.
The vertical axis (Y-axis) runs up and down.
Leave room for axis labels
2. Label the Axes
How do you know which variable
goes on each axis?
The manipulated variable goes on the X- axis
The responding variable goes on the Y-axis Manipulated
Variable
Resp
ond
ing
Vari
ab
le
3. Create a Scale Determine the range of the values for each
axis. The range usually goes from zero to the
highest value of the variable. A pattern of numbers must be established for
each axis. Each grid line must be evenly spaced.oLook for patterns in the data like 2’s, 5’s
10’s, 100’s, etc.oThe scale will depend on how much
space you have to graphoBoth scales should begin at zero when
possible.
Setting up the Graph Steps 1–3
Write MV on X
Wri
te R
V o
n
Y
Number each axis…Must be evenly
spaced…
2 4 6 8 10 12 14
5 1
0 1
5 2
0 2
5 30
Time
(sec)
Distance (m)
2 5
4 10
6 15
8 20
10 25
12 30
4. Plot the Points
Plot a point for each piece of data (ordered pairs).
Use the grid lines to locate where each pair will intersect.
Start with the first pair of values and continue to the last.
5. Connect the Points with a Line
or Draw a line of “Best Fit” Look at the plotted points to identify a general pattern in the data.
Connect each point with a ruler. Sometimes you will be asked to draw a line
that comes close to all the points. This is called the “line of best fit”
The best fit line by be straight or curved.o Straight line (Linear graph) – use a ruler
to connect points with one straight line.o Curved line (nonlinear graph) – sketch
slowly through general direction of points.
Connecting the Points
Best Fit Lines
6. Title the Graph Add a title that identifies the
variables or relationship in the graph.
Use the subtitles on the X and Y axes to form the main title.
If a graph has more than one line it needs a key.
Setting up the Graph Steps 4–6
2 4 6 8 10 12 14
5 1
0 1
5 2
0 2
5 30
Time (min)
Dis
tance
(m
)
Time
(sec)
Distance (m)
2 5
4 10
6 15
8 20
10 25
12 30
Distance vs. Time
Calculating Slope The slope of a graph line tells
you how much “Y” changes for every change in “X”.
Slope formula = “rise over run”Y2 – Y1
X2 – X1
Interpreting Graphs 1. What is the line graph about?
2. What is the responding variable?
3. What is the busiest time of day at the store?
1. The number of people in a store during different hours of the day2. The number of people
3. 1 pm
4. At what time does business start to dramatically slow down?
5. How many people are in the store when it opens?
6. About how many people are in the store at 2:30 pm?
4. After 2pm
5. 2 people
6. 10 people
7. What time had the greatest number of people in the store?
8. What
time had the least number of people in the store?
7. 1 pm
8. 10 am
Graph Animation http://www.physicsclassroom.com/mmedia/kinema/fs.cfm