DA0-002 Visualization and Reporting Practice Question
An analyst creates a scatter plot with three variables: X, Y, and a third variable represented by the size of the markers. This chart is called a:
⚠ Common exam trap
Many candidates confuse a bubble chart with a heat map because both can represent three variables, but the heat map uses color gradients on a grid, not marker size on a scatter plot.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Bubble chart
A bubble chart is a variation of a scatter plot where a third numeric variable is encoded by the size (area) of the markers. This allows the visualization of three dimensions of data simultaneously on a two-dimensional plane, making it the correct choice for the described chart.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Heat map
Why it's wrong here
A heat map encodes a third variable as colour intensity across a matrix of two categorical or binned axes, not as marker size on a continuous scatter. It is tempting because both add a third dimension visually, but heat maps suit density or correlation matrices rather than X–Y point plots.
- ✗
Treemap
Why it's wrong here
A treemap encodes hierarchical part-to-whole data as nested rectangles sized by value, so it cannot plot two continuous axes with a third size dimension. It is tempting because marker size also encodes magnitude, but treemaps suit proportional category breakdowns, not X–Y correlation with a bubble variable.
- ✓
Bubble chart
Why this is correct
A bubble chart extends the scatter plot by encoding a third variable as marker size, so each point conveys three dimensions simultaneously. X and Y position the data point while the bubble's magnitude represents the additional measure, matching the described visual encoding exactly.
- ✗
Waterfall chart
Why it's wrong here
A waterfall chart displays sequential positive and negative contributions to a running total, so it cannot encode three variables via X, Y and marker size. It is tempting because waterfall charts are genuinely useful for decomposing cumulative change, such as showing how individual revenue streams build to a net profit figure.
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