Data Visualization MCQS
Q. What is data visualization?
Solution:
Data visualization encodes data as visual elements — position, length, color — so patterns and trends are immediately visible.
Q. Which chart type is best for showing a trend over time?
Solution:
Line charts display data points connected along a continuous axis (typically time), making them ideal for showing upward/downward trends and seasonality.
Q. What does a scatter chart show?
Solution:
Scatter charts plot two numeric values against each other, revealing whether they are positively correlated, negatively correlated, or uncorrelated.
Q. Which Python library is most commonly used for basic data visualization?
Solution:
Matplotlib is the foundational Python plotting library; Seaborn and Plotly build on it for more specialized or interactive visuals.
Q. What is the purpose of conditional formatting in data visualization?
Solution:
Conditional formatting applies visual cues (color, icons, data bars) based on values, helping viewers spot high/low performers at a glance.
Q. In Power BI, what is the difference between a Table and a Matrix visual?
Solution:
A Matrix works like a pivot table with expandable/collapsible row and column groupings, while a Table displays a flat, spreadsheet-like grid.
Q. Which of the following is NOT a common data visualization tool?
Solution:
SQL Server Management Studio is a database management tool, not a visualization tool. Power BI, Tableau, and Matplotlib are all designed for creating visual representations of data.
Q. Why does visual perception research recommend bar charts over pie charts for comparing quantities?
Solution:
Perceptual research (Cleveland & McGill) shows position-on-a-common-scale judgments are more accurate than angle judgments, making bar charts more precise for comparison tasks.
Q. What is IoT data visualization primarily used for?
Solution:
IoT visualization displays live sensor readings, threshold alerts, and time-series trends from connected devices, enabling real-time operational monitoring.
Q. What does a combo chart combine?
Solution:
A combo chart merges columns and a line to show two related measures — for example, revenue (columns) and margin percentage (line) — making dual-metric comparisons easy.
Q. What does KPI stand for?
Solution:
KPI stands for Key Performance Indicator — a measurable value that shows how effectively a goal is being met.
Q. How many KPIs should a well-designed dashboard typically show?
Solution:
Best practice recommends 4-8 KPIs so the viewer can scan the dashboard in seconds without information overload.
Q. Where should the most important KPI be placed on a dashboard?
Solution:
The eye naturally starts at the top-left and scans in an F-pattern, so the headline KPI should be placed there.
Q. In Power BI, what is the difference between a Dashboard and a Report?
Solution:
Power BI Dashboards are single-page, pinned-tile views in the Service; Reports are multi-page, interactive files built in Desktop and published to the Service.
Q. What is the purpose of adding a 'last refreshed' timestamp to a KPI dashboard?
Solution:
 last refreshed’ timestamp lets viewers know the data’s freshness, which is critical for decision-making — stale data can lead to wrong conclusions.
Q. Which visual type is best for showing a single metric vs. a target?
Solution:
kPI cards show a value vs. target with a trend indicator; gauges show progress on a radial dial — both are purpose-built for single-metric-vs-target display.
Q. A dashboard has 15 KPIs and requires scrolling. What should you do?
Solution:
A dashboard should fit on one screen. Move secondary metrics to drill-through pages so the dashboard stays focused on the headline KPIs
Q. Why should green/red color be used purposefully rather than decoratively on a KPI dashboard?
Solution:
Green/red triggers an instant good/bad judgment. Using it decoratively dilutes the signal and is inaccessible to colorblind viewers unless paired with an icon or label.
Q. What is the most common data visualization mistake?
Solution:
Chart-type mismatch is the most frequent mistake — a pie chart for 12 categories or a line chart for unordered data immediately misleads viewers.
Q. Why should bar charts almost always start the Y-axis at zero?
Solution:
Bar chart comparison relies on length perception. Starting above zero makes small differences look dramatic and large ones look trivial.
Q. What is 'chart junk'?
Solution:
Chart junk refers to non-data ink — visual elements that don’t convey information but clutter the chart and can distort perception.
Q. What percentage of men have red-green color vision deficiency?
Solution:
 Approximately 8 % of men (and 0.5 % of women) have red-green color vision deficiency, making red/green-only color coding inaccessible for a significant audience.
Q. A chart is titled simply 'Revenue.' What should it say instead?
Solution:
 A descriptive title states the measure, dimension, and time period so the viewer immediately knows what they are looking at.
Q. A dashboard has 18 visuals on one page. What is the best corrective action?
Solution:
Keeping 6-8 visuals avoids clutter while drill-through pages preserve access to secondary metrics for viewers who need them.
Q. How many core colors should a dashboard color theme typically use?
Solution:
A palette of 3-5 core colors reduces cognitive load while providing enough variation for different data series and semantic meanings
Q. Why should red and green be reserved for semantic meaning on dashboards?
Solution:
Red = below target and green = above target are near-universal conventions. Using them as decoration confuses viewers and is inaccessible to colorblind users.
Q. In Power BI, how do you apply a custom color theme?
Solution:
Custom themes are applied via View → Themes → Browse and accept a JSON file that sets dataColors, background, foreground, and other visual defaults.
Q. What contrast ratio does WCAG recommend for text on dashboards?
Solution:
WCAG AA requires at least 4.5:1 contrast between text and its background for normal-sized text, ensuring readability for viewers with low vision.
Q. A dashboard uses a 10-color palette with several similar shades. What is the risk?
Solution:
Similar shades are hard to distinguish, especially under sub-optimal viewing conditions (projectors, small screens, color vision deficiency). Fewer, more distinct colors improve accuracy.
Q. Why is a dark background theme risky for dashboards shared widely?
Solution:
Dark themes can look polished on good screens but fail on projectors, printed copies, and for users with certain visual impairments if contrast isn’t rigorously tested.
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