Interpreting Graphs Why bother with graphs Line Graphs
Interpreting Graphs ü Why bother with graphs? üLine Graphs üConstructing Line Graphs üBar Graphs üPie charts üScatter plots
How to Interpret Graphs
Why are graphs useful? Graphs are a quick way to visualize trends or to make comparisons.
Graphs provide a visual, as opposed to text.
Looks like all those hours of science class paid off
Types of Graphs Line graphs- used to measure data over time Bar graphs- used to compare values Pie charts- used to compare values (usually percentages) Scatter plots- used to show trends and relationships among a large number of data There are typically two variables that you “map out” when graphing. -The respondent variable- what is being measured/observed -The independent (manipulated) variable- what is changed during the experiment to invoke a change in the respondent.
This is a simple line graph charting temperature. Temperature is labeled on the "y" axis and the dates (Jan 1 -7) is labeled on the "x" axis. During the first week of January, which day was the coldest? January ______1 st What was the temperature on o F ~39 January 7 th? ______ Which day does the temperature peak? ____ January 4 th The respondent variable is the temperature, the independent variable are the dates.
Number of Frogs Practice Constructing a Line Graph 150 140 Data to graph: Year 0 - 10 frogs Year 5 - 20 frogs Year 10 - 60 frogs Year 15 - 120 frogs Year 20 - 120 frogs Time or trials are always placed on the x-axis 130 120 110 100 90 80 70 60 50 40 30 20 The variable goes on the Y axis. 10 0 5 10 Year 15 20 Your numbers MUST be evenly spaced for accuracy.
What if time isn’t a variable on your graph? Distance (m) Usually the X axis has the independent variable (what you can manipulate or adjust) and the Y has the responding variable (what is measured/counted/observed) Multiple carts are pushed down a track with different sized weights attached to them. The distance traveled was measured. 100 90 Weight 80 70 60 50 40 30 20 10 1 2 3 4 5 6 Weight (kg) 7 1 kg 2 kg 3 kg 4 kg 5 kg 6 kg 7 kg Distance 150 m 140 m 120 m 90 m 70 m 50 m 30 m
Line graphs can have multiple lines
Practice: What if the data is not so easy to place? Temperature & Number of turtle eggs hatched (out of 20) 60 degrees = 3 eggs 62 degrees = 4 eggs 65 degrees = 7 eggs 69 degrees = 11 eggs 72 degrees = 16 eggs 75 degrees = 17 eggs Before you begin, what goes on your axes? Temperature range= 60 -74 Hatchling range= 3 -17
Graphs show us trends and relationships among data. There are generally two types of relationships that data will exhibit: inverse and direct. If one variable increases and the other decreasesthey share an inverse relationship. If both variables increase or decrease together- they share a direct relationship.
Inverse Relationships- As one variable increases, the other factor decreases. Examples) As you exercise more, your risk for heart disease decreases. The farther I drive, the less distance I have to reach my destination.
Direct relationships occur when the two variables increase or decrease together. Examples: The higher your temperature, the higher your perspiration rate is. As the diameter of a pipe increases, the flow of water through the pipe also increases.
Direct or Inverse? Refer to your practice line graphs. Frogs vs. Time- direct or inverse (circle one). Weight vs. Distance- direct or inverse (circle one)
Bar Graphs are used to compare values. What is the most common shoe length? ______ 27 cm What is the least common shoe length? ______ 21, 29, 30, 31 cm How many people have shoes that are 26 cm long? ____ 2
Pie charts are also used to compare values (usually as a percentage but not always).
What can you expect to spend most of your time doing at Disneyland? What can you expect to spend least of your time doing at Disneyland?
Roughly what percent of Federal spending does national defense account for? ~20% Roughly what percent does our nation spend on education? ~4%
Scatterplots are used to compare trends among many data points.
age What do each of the dots represent? ________ ~43 Approximately how old are husbands of 40 yo wives? ______ ~65 Approximately how old are wives of 70 yo hubsands? ______ ~38 -44 MOST ages lie within which range? ________
For each scenario, choose which type of graph would be best to use (line, bar, pie, or scatter plot). 1. To show eating vegetables over a 10 year period can lower cholesterol. ________ Line graph 2. To compare the leg lengths and antennae lengths of crickets. __________ bar graph 3. To analyze the relationship between hours studying for a test and test scores among students. _______ Scatter plot 4. To show the percentages of students in class that are male vs. female ________. Pie chart 5. To compare the salaries of 4 different professions: teacher, veterinarian, software engineer, banker ____ bar graph
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