Yesterday we used Google Sheets to practice making Bar Graphs, which you will recall are best for comparing unlike things, or things that belong to different categories (like boys vs. girls, 6th grade vs. 7th grade, UK vs. UL, or the Top 10 Tallest Mountains in the Solar System). The x-axis (horizontal/left-to-right) is usually qualitative data.
Q: Is the x-axis of a Bar Graph always qualitative data? Can you think of a counterexample to falsify, or disprove, this hypothesis?
Today we're going to be talking about Line Graphs. Line graphs are used to show how one variable changes over time (or how two continuous variables are connected). The key is, unlike bar graphs that compare things from different categories, line graphs pretty much show how one thing changes under different conditions.
Down the side of this page are a half-dozen line graphs.
Notice how the first three illustrate one single variable (temperature, car value, number of people in a store) and show how that changes at different times (different days, different years, different hours of the day).
Take a look at the fourth graph illustrating Sam's weight. Are the values on the x-axis quantitative or qualitative?
Do they still represent time? Even if they didn't, they're still part of a continuous series.
Take a look at the last graph, showing teens with cell phones. What is the variable shown on the x-axis? Is it part of a continuous series?
Consult with your neighbor to see if you can think of another continuous series. (Bonus points if it is not directly related to time!)
Below you'll see a Data Table representing the number of Spaceflights Launched by The Soviet Union/Russia and the United States in each decade of the past half-century.
Log-in to Google Sheets (using your school e-mail and password) and enter the data to generate a line graph.
Q: How many different lines are there going to be?
(Hint: How many different variables are you showing changing over time?)
Customize the line color to match the Data Table.
Q: Do you need to use a Legend for this graph?