MS-DS Master of Data science Data Visualization and Communication 5 — Questions and Answers
Question 1: In Tableau, what is the difference between a 'dimension' and a 'measure' by default?
- Dimensions are always dates; measures are always integers
- Dimensions are categorical fields used for grouping/slicing; measures are numeric fields that are aggregated (Correct answer)
- Dimensions appear on the x-axis only; measures appear on the y-axis only
- Dimensions require a spatial join; measures require a time join
Correct answer: Dimensions are categorical fields used for grouping/slicing; measures are numeric fields that are aggregated
Tableau classifies discrete categorical fields as dimensions (used to partition data) and continuous numeric fields as measures (aggregated via SUM, AVG, etc.).
Question 2: A scatter plot shows a strong visual correlation between ice cream sales and drowning rates. What concept does this best illustrate in data communication?
- Simpson's paradox
- Confounding — a lurking variable (hot weather) drives both (Correct answer)
- Berkson's bias
- Regression to the mean
Correct answer: Confounding — a lurking variable (hot weather) drives both
Both variables are driven by a common cause (summer heat), making them spuriously correlated — a classic confounding example used in data literacy education.
Question 3: Which perceptual ranking (from most to least accurate) correctly reflects Cleveland and McGill's hierarchy for quantitative judgments?
- Area → length → angle → position on common scale
- Position on common scale → length → angle → area (Correct answer)
- Color → position → length → area
- Angle → area → length → position on common scale
Correct answer: Position on common scale → length → angle → area
Cleveland & McGill's 1984 experiments found that people most accurately judge position on a common scale, then length, then angle, with area and color being least accurate.
Question 4: What does 'progressive disclosure' mean in the context of interactive data dashboards?
- Displaying data incrementally as the server loads it
- Revealing detail on demand (drill-down, tooltip, filter) rather than showing everything at once (Correct answer)
- Disclosing data sources in a footnote progressively as the user scrolls
- Gradually fading in chart elements using CSS animations
Correct answer: Revealing detail on demand (drill-down, tooltip, filter) rather than showing everything at once
Progressive disclosure keeps dashboards uncluttered by showing summary information upfront and allowing users to access deeper detail only when they request it.
Question 5: A radar (spider) chart is generally considered problematic for data communication. Which is the primary reason?
- It cannot handle more than three variables
- Area perception is non-linear and axis order arbitrarily affects the polygon shape, making comparison difficult (Correct answer)
- It requires polar coordinates unavailable in most BI tools
- It can only display integer values
Correct answer: Area perception is non-linear and axis order arbitrarily affects the polygon shape, making comparison difficult
Reordering the axes changes the polygon shape even with identical data, and humans poorly judge areas of irregular polygons, making radar charts prone to misinterpretation.
Question 6: When applying the 'SIFT' framework for evaluating data sources before visualizing them, what does the 'I' stand for?
- Interval (temporal resolution)
- Investigate the source (Correct answer)
- Index (normalize the data)
- Interpret outliers first
Correct answer: Investigate the source
SIFT (Stop, Investigate the source, Find better coverage, Trace claims) is a media literacy framework; 'I' means investigating who produced the data and why.
Question 7: In accessible data visualization, what is the purpose of providing an 'alt text' description alongside a chart image?
- To improve SEO ranking of the page
- To convey the chart's key insight to screen-reader users who cannot see the image (Correct answer)
- To store the raw data in the HTML for machine parsing
- To display a caption below the chart in all browsers
Correct answer: To convey the chart's key insight to screen-reader users who cannot see the image
Alt text for charts should describe the type of chart and its key finding so blind and low-vision users consuming the page via screen readers receive equivalent information.
MS-DS Master of Data science Data Visualization and Communication 5
In Tableau, what is the difference between a 'dimension' and a 'measure' by default?