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Graphing Data
3 Types of Graphs
• Bar Graph• Line Graph• Circle (or Pie) Graph
Bar Graph
Useful for graphing items with different categories
Bar Graph
“Game of Life” Salaries
0
10000
20000
30000
40000
50000
60000
Business Teacher Journalist Doctor
I can change the order.
Bar Graph
“Game of Life” Salaries
0
10000
20000
30000
40000
50000
60000
Doctor Journalist Teacher Business
Does this change the information?
Bar Graph
“Game of Life” Salaries
0
10000
20000
30000
40000
50000
60000
Business Doctor Journalist Teacher
Whatever helps me get the point across
Circle Graph
Satisfaction with the Temperature in Mr. Jackson’s
Room5% 2%
53%
40%
Too Cold
Too Hot
UndecidedJust Right
Ideal for showing percentages(fractions)
All the parts add up to a whole
To find the percentage
• Divide the number in whichever category by the total number.– 10 students are too hot– 12 students are too cold– 2 students aren’t sure– 1 Teacher thinks it is just right
• The total is 25
To find the percentage
• 10/25 = 40% are too hot• 12/25 = 48% are too cold• 2/25 = 8% aren’t sure• 1/25 = 4% is just right
• When making the graph:– 1 circle is 360° = 100%– Each percent is 3.6°
Line graph
• A line graph is useful when a dependent variable changes due to a relationship with an independent variable.
• The independent variable is “x”• The dependent variable is “y”
Line graph
• We’ll start with an experiment.
Line graph
• As we turn the knob, we will take data. The knob location will be x, and the gauge reading will be y.– x=½ and y=0– x=1 and y=1– x=2 and y=3– …and so on
Let’s look at our data
• Let’s make a table with our data.
• It may be helpful to sort the data by the independent variable.
X Y½ 01 12 30 -1-1 -3
X Y-1 -30 -1½ 01 12 3
Let’s look at our solutions
• Now let’s plot the solutions on a graph.
X Y-1 -30 -1½ 01 12 3
Tow the line!
• It is reasonable to use the line as the solution rather than just the points.– Interpolation– Extrapolation
If it doesn’t fit…
• Usually, real data doesn’t fit on a perfect line.
• DO NOT play “connect the dots”.
• Make a “regression” line, or “best fit” line.
0
0.5
1
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0 1 2 3 4 5 6
WRONG
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1
1.5
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2.5
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0 1 2 3 4 5 6
If it doesn’t fit…
• Usually, real data doesn’t fit on a perfect line.
• DO NOT play “connect the dots”.
• Make a “regression” line, or “best fit” line.– “Eyeball” it– Use Excel 0
0.5
1
1.5
2
2.5
3
0 1 2 3 4 5 6
It doesn’t look square!
• We won’t always have a straight line on a graph.
• This is a parabola. It is common in science graphs.
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It doesn’t look like anything!
• Often, we can write an equation for a graph.
• Sometimes we can’t.
• That’s okay.
-4
-2
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Assignment
• p. 26, 1-5• Worksheet
• Chapter 1 Test Friday 8/27
• Bring Index Cards tomorrow