Data Science Questions Section 1: Data Visualization & BI Tools (Power BI, Tableau, etc.)

Data Science Questions in Section 1 focus on the essential concepts of Data Visualization and Business Intelligence (BI) tools such as Power BI, Tableau, and others. This section is designed to test a candidate’s understanding of how data can be transformed into meaningful insights using visual storytelling and interactive dashboards. Mastery of these tools is crucial for any data professional aiming to communicate findings clearly and drive data-driven decisions across organizations.

Also Read: Optum Interview Questions: 30 Multiple Choice Questions (MCQs) with Answers

Q. What is the difference between a calculated column and a measure in Power BI?

• Measures are stored in memory; calculated columns are recalculated with each filter
• Calculated columns are used in row context, measures in filter context
• Measures create new rows; calculated columns summarize data
• No difference
  
  Answer: Calculated columns are used in row context, measures in filter context

Q. Which function creates a Year-To-Date measure in DAX?

• YTD()
• SUMYTD()
• TOTALYTD()
• YTD_SUM()
  
  Answer: TOTALYTD()

Q. How do you connect a Date Table to a Sales table in Power BI for YTD calculations?

• No relationship is required
• By manually entering date values
• By creating a relationship on the date field
• Use a slicer only
  
  Answer: By creating a relationship on the date field

Q. In Tableau, which field do you place on the X-axis to create a line chart of sales over time?

• Sales
• Category
• Date
• Region
  
  Answer: Date

Q. What is the difference between live and extract connections in Tableau?

• Extracts show real-time data
• Live connections update automatically
• Extracts require SQL knowledge
• No Major difference
  
  Answer: Live connections update automatically

Q. Which of these improves dashboard performance?

• Using too many visuals
• Disabling filters
• Minimizing use of high-cardinality fields
• Increasing screen size
  
  Answer: Minimizing use of high-cardinality fields

Q. What is the role of a data dictionary in dashboard creation?

• To store formulas
• To define calculations
• To document definitions and business logic
• Not useful
  
  Answer: To document definitions and business logic

Q. Which of the following is a reason to use Level of Detail (LOD) expressions in Tableau?

• To create duplicate rows
• To filter views
• To fix aggregations at different levels
• To join tables
  
  Answer: To fix aggregations at different levels

Q. LOD Expression Example: To calculate average claim amount per doctor, regardless of specialty, use:

• {FIXED [Doctor ID]: AVG([Claim Amount])}
• {INCLUDE [Specialty]: SUM([Claim Amount])}
• {EXCLUDE [Doctor ID]: COUNT([Claims])}
• ALL [Doctor ID]: MAX([Claim Amount])}
  
  Answer: {FIXED [Doctor ID]: AVG([Claim Amount])}

Q. Which technique blends data from two sources in Tableau?

• SQL UNION
• Merge Join
• Data Blending
• Grouping
  
  Answer: Data Blending

Q. Which join does Tableau use by default when blending data?

• Inner Join
• Left Join
• Right Join
• Full Outer Join
  
  Answer: Left Join

Q. What is the use of primary and secondary data sources in Tableau blending?

• They allow for duplicate charts
• They enable relational joins
• They define blending logic
• No use
  
  Answer: They define blending logic

Q. Which of these improves data quality before dashboarding?

• Skipping null values
• Validating source fields
• Random sampling
• Avoiding transformations
  
  Answer: Validating source fields

Q. How do you collaborate with business users during dashboard development?

• Build dashboard first, then ask for feedback
• Validating source fields
• Let users design UI themselves
• No collaboration needed
  
  Answer: Validating source fields

Q. Which practice helps manage ambiguous requirements?

• Wait until clarity
• Escalate to manager immediately
• Break down into smaller user stories
• Skip the task
  
  Answer: Break down into smaller user stories

Q. Virtual warehouses in Snowflake help in:

• Storage
• UI design
• Compute scaling
• User management
  
  Answer: Compute scaling

Q. How do you scale virtual warehouses in Snowflake?

• Adding disk space
• Switching from extract to live
• Modifying cluster size or using multi-cluster
• Enabling indexing
  
  Answer: Modifying cluster size or using multi-cluster

Q. What is a context filter in Tableau?

• A temporary filter
• A primary filter that improves performance
• Used only with maps
• Does not affect performance
  
  Answer: A primary filter that improves performance

Q. Power BI relationships are best defined between:

• Measures
• Calculated tables
• Keys/IDs
• Slicers
  
  Answer: Keys/IDs

Q. To reduce Tableau dashboard load time, you can:

• Use multiple joins
• Use live connection only
• Limit use of quick filters
• Increase row count
  
  Answer: Limit use of quick filters

Q. What’s the first step in creating dashboards for stakeholders?

• Share dashboard immediatel
• Build visuals
• Understand requirements
• Create calculated fields
  
  Answer: Understand requirements

Q. One of the key components of good dashboard UX is:

• Dark themes
• Fewer visuals with clear insights
• No filters
• Use of animations
  
  Answer: Fewer visuals with clear insights

Q. Which of the following defines a KPI?

• Key Performance Indicator
• Key Price Index
• Knowledge Performance Integration
• Known Public Insight
  
  Answer: Key Performance Indicator

Q. Which of the following Tableau fields is discrete?

• Sales
• Quantity
• Region
• Profit Ratio
  
  Answer: Region

Q. To mentor junior analysts, the best approach is:

• Assign complex tasks early
• Conduct weekly check-ins and pair programming
• Avoid explaining basics
• Let them learn independently
  
  Answer: Conduct weekly check-ins and pair programming

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