Build data tables and graphs
Organize measurements into a labeled table, then pick and label the graph that fits the data.
- Reading units and labels: A data table is only usable if each column says what was measured and in what unit.
- Categorical vs. numerical data: Whether data is categories or numbers decides which graph type fits.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Put measurements into a labeled table, then match the graph to the data: categories to a bar graph, change over time to a line graph, two numeric measurements to a scatter plot.
The table shows the lead reading at four different neighborhood taps. Which graph type best displays this data?
Reviewed| Site | Lead concentration (ppb) |
|---|---|
| Site A | 8 |
| Site B | 21 |
| Site C | 5 |
| Site D | 14 |
- A.A line graph, because it shows change over time
- B.A bar graph, because it compares a measurement across separate categories
- C.A scatter plot, because both axes are numeric
- D.A pie chart, because the values are percentages
Show the worked solution ▾
Answer: B. A bar graph, because it compares a measurement across separate categories
- Step 1: Identify the data type: The first column lists separate categories (four different sites); each has one lead reading. There is no time axis.
- Step 2: Match the graph: Comparing one measurement across separate categories is exactly what a bar graph does.
Why it's right: The sites are separate categories with one reading each, so a bar graph: comparing a measurement across categories: fits best.
- A: A line graph needs time (or another continuous scale) on the horizontal axis, which this table does not have.
- C: A scatter plot needs two numeric measurements per point; here one axis is a category (the site).
- D: The values are concentrations, not parts of a whole, so a pie chart does not fit.
Aligned to HBS data presentation: choosing a graph · reading level ~grade 9
- A water report graphs lead by sampling site as bars so readers can compare locations at a glance.
Fill these in as you work through the lesson.
- Data table (rows and columns of organized measurements):
- Column header (names what was measured):
- Unit (tells you the scale of the number):
- Bar graph (best for comparing categories):
- Line graph (best for a value changing over time):
Every column in a data table needs a and a . Compare categories with a graph, show change over time with a graph, and compare two numeric measurements with a plot.
- What two things must every data-table column show?
- You compare lead levels at four different sites. Which graph type fits?
- You track a patient's blood lead level once a month for a year. Which graph type fits?
You have lead readings (in ppb) from four neighborhood taps. Build a two-column table with proper headers and units, then say which graph type fits and what goes on each axis.