Microsoft 70-778: Analyzing and Visualizing Data with Microsoft Power BI — Questions and Answers

Question 1: What does the 'Pivot Column' transformation do in Power Query?

Aggregates a column into a single value
Converts a column to a different data type
Rotates rows into columns based on a key column
Converts attribute-value rows into separate columns (Correct answer)

Correct answer: Converts attribute-value rows into separate columns

Pivot Column turns unique values from one column into new column headers, essentially transposing key-value pairs into a wide table.

Question 2: In Power BI, which view allows you to see the raw data stored in each table?

Query editor
Data view (Correct answer)
Report view
Model view

Correct answer: Data view

Data view displays the actual rows and columns of data stored in each table of your Power BI model.

Question 3: What is context transition in DAX?

Transitioning data between Import and DirectQuery modes
Converting row context into filter context when CALCULATE is called inside a row iteration (Correct answer)
Converting filter context to row context using CALCULATETABLE
Switching between report pages

Correct answer: Converting row context into filter context when CALCULATE is called inside a row iteration

Context transition occurs when CALCULATE is called inside a row context, automatically converting that row context into an equivalent filter context.

Question 4: Which DAX time intelligence function calculates year-to-date totals?

SAMEPERIODLASTYEAR
DATESQTD
TOTALYTD (Correct answer)
DATESMTD

Correct answer: TOTALYTD

TOTALYTD evaluates an expression from the beginning of the year up to the last date in the current filter context.

Question 5: What does the DAX function CALCULATE do?

Evaluates an expression in a modified filter context (Correct answer)
Returns the first value in a column
Sums values in a column
Counts rows in a table

Correct answer: Evaluates an expression in a modified filter context

CALCULATE evaluates a DAX expression after applying the specified filter modifications to the current filter context.

Question 6: What does 'Merge Queries' do in Power Query?

Combines all columns from all tables
Joins two tables horizontally on a common key column (Correct answer)
Removes matching rows from one table
Stacks rows from two tables vertically

Correct answer: Joins two tables horizontally on a common key column

Merge Queries performs a join between two tables based on matching key columns, similar to a SQL JOIN.

Question 7: What does the USERELATIONSHIP function do in DAX?

Activates an inactive relationship for use within a CALCULATE expression (Correct answer)
Creates a new relationship between two tables
Lists all relationships in the model
Disables an existing active relationship

Correct answer: Activates an inactive relationship for use within a CALCULATE expression

USERELATIONSHIP activates an inactive relationship within the scope of a CALCULATE expression to use an alternate join path.

Question 8: What is the purpose of the 'Viewer' role in a Power BI workspace?

Can create and publish reports in the workspace
Can view and interact with reports and dashboards but cannot edit or publish (Correct answer)
Can manage workspace settings and member access
Can export data from all datasets in the workspace

Correct answer: Can view and interact with reports and dashboards but cannot edit or publish

Viewers can consume (read and interact with) reports and dashboards but have no editing, publishing, or administrative capabilities.

Question 9: Which Power Query step removes rows where a specified column's value is null?

Fill Down
Filter Rows (Correct answer)
Remove Errors
Remove Duplicates

Correct answer: Filter Rows

Filter Rows allows you to filter out rows based on conditions, including removing rows where a column value is null.

Question 10: Which Power BI feature enables governance by allowing admins to enforce policies on workspace creation and sharing?

Power BI Embedded
Power BI Desktop settings
Power BI Gateway
Power BI Admin Portal (Correct answer)

Correct answer: Power BI Admin Portal

The Power BI Admin Portal provides tenant-level settings allowing administrators to control feature access, sharing policies, and workspace governance.

Question 11: What is a 'dataflow' in Power BI?

A data export workflow to SharePoint
A reusable set of Power Query transformations stored in the Power BI Service (Correct answer)
A real-time data stream from IoT devices
A data pipeline from Azure Data Factory

Correct answer: A reusable set of Power Query transformations stored in the Power BI Service

Dataflows store reusable Power Query ETL logic in the cloud, allowing multiple datasets and reports to share the same transformation logic.

Question 12: What is 'report page tooltips' in Power BI?

Displaying column descriptions in a table visual
Using a full report page as a custom tooltip shown when hovering over a visual (Correct answer)
Adding tooltips to slicer items
Adding text annotations to a report page

Correct answer: Using a full report page as a custom tooltip shown when hovering over a visual

Report page tooltips let you design a separate report page that appears as a rich tooltip when users hover over a visual.

Question 13: In DAX Studio's Server Timings pane, what does a disproportionately high Formula Engine (FE) time relative to Storage Engine (SE) time typically indicate?

The data source connection is slow
The report has too many visuals on one page
The dataset exceeds the Power BI Pro size limit
The DAX contains complex iterating logic the storage engine cannot fully handle (Correct answer)

Correct answer: The DAX contains complex iterating logic the storage engine cannot fully handle

High FE time indicates the DAX uses operations like row-by-row iteration (SUMX, FILTER) that the VertiPaq storage engine cannot satisfy with a simple column scan, requiring more formula engine cycles.

Question 14: In Power BI Premium, which feature enables Import mode for historical data partitions while using DirectQuery for the most recent real-time partition of the same table?

Live Connection with caching
Dual storage mode
Incremental refresh with hybrid tables (Correct answer)
Composite model

Correct answer: Incremental refresh with hybrid tables

Hybrid tables extend incremental refresh so that historical partitions are stored in Import mode for speed, while the latest partition uses DirectQuery to serve real-time data without a full refresh.

Question 15: In Power BI, what is a 'role-playing dimension'?

A dimension table used for user access control
A single dimension table used multiple times with different relationships (Correct answer)
A dimension that drives row-level security
A dimension that stores user role names

Correct answer: A single dimension table used multiple times with different relationships

A role-playing dimension is a single table (e.g., a Date table) connected to a fact table multiple times via inactive relationships.

Question 16: What is a Power BI App?

The Power BI Desktop application
A Power BI integration with Microsoft Teams
A mobile version of a Power BI report
A packaged collection of dashboards and reports distributed to consumers in the Power BI Service (Correct answer)

Correct answer: A packaged collection of dashboards and reports distributed to consumers in the Power BI Service

A Power BI App bundles dashboards and reports from a workspace into a polished package distributed to a wide audience.

Question 17: What is a common performance drawback of excessive bidirectional cross-filtering in a Power BI data model?

It can create ambiguous filter paths, leading to slower queries and unexpected results (Correct answer)
It forces all tables into DirectQuery mode
It prevents the use of calculated columns
It reduces the number of available DAX functions

Correct answer: It can create ambiguous filter paths, leading to slower queries and unexpected results

Bidirectional cross-filtering multiplies the filter propagation paths the engine must evaluate, causing ambiguity and performance degradation in complex models.

Question 18: You have a Microsoft Excel spreadsheet with a Sales table in it. <br> The Sales table must be added as a tile to a Power BI dashboard. <br> What is the best way to set up the tile?

Import the data from the Excel workbook into the Power BI service
Publish the workbook to the Power BI service from Excel
Pin the table from the Power BI tab in Excel (Correct answer)
Upload the Excel workbook to the Power BI service

Correct answer: Pin the table from the Power BI tab in Excel

The most efficient way to add a table from an Excel spreadsheet as a tile to a Power BI dashboard is by using the Power BI tab (or add-in) directly within Excel. This feature allows users to select a range, chart, or table in their Excel workbook and 'Pin' it to an existing Power BI dashboard. This creates a live tile that updates as the Excel data changes, without requiring a full import of the workbook into the Power BI service.

Question 19: What is the purpose of a waterfall chart in Power BI?

Mapping geographic data
Showing correlation between two variables
Displaying cumulative effects of sequential positive and negative values (Correct answer)
Comparing categories side by side

Correct answer: Displaying cumulative effects of sequential positive and negative values

A waterfall chart shows how a series of positive and negative values cumulatively contribute to a final total.

Question 20: Which data type in Power Query stores whole numbers without decimal places?

Text
Fixed Decimal Number
Decimal Number
Whole Number (Correct answer)

Correct answer: Whole Number

Whole Number data type in Power Query stores integers (positive and negative whole numbers) without any decimal precision.

Question 21: Which Power Query transformation splits a column into multiple columns based on a delimiter?

Extract
Parse
Pivot Column
Split Column (Correct answer)

Correct answer: Split Column

Split Column divides a column into multiple columns using a specified delimiter like a comma, space, or custom character.

Question 22: What is the purpose of the DIVIDE function in DAX?

Divides two numbers and returns an error if denominator is zero
Rounds a division result to two decimal places
Converts a fraction to a percentage
Divides two numbers safely, returning an alternate result if denominator is zero (Correct answer)

Correct answer: Divides two numbers safely, returning an alternate result if denominator is zero

DIVIDE safely handles division by zero by returning an optional alternate result instead of throwing an error.

Question 23: What does 'Dual' storage mode mean for a table in Power BI?

The table is stored in two databases
The table can act as either Import or DirectQuery depending on the query (Correct answer)
The table has two primary keys
The table exists in both Power BI Desktop and Service

Correct answer: The table can act as either Import or DirectQuery depending on the query

Dual mode allows a table to behave as Import or DirectQuery depending on whether the query requires cached or live data.

Question 24: What is the purpose of a 'Parameter' in Power Query?

A column alias for reporting
A variable value that can be used dynamically within query steps (Correct answer)
A fixed threshold for filtering rows
A connection string stored securely

Correct answer: A variable value that can be used dynamically within query steps

A Power Query Parameter is a reusable variable that can be used in query steps, source paths, or filter conditions.

Question 25: What Power BI feature allows you to test which data a specific user or role would see under RLS?

'View as role' in Power BI Desktop or Service (Correct answer)
Role simulator in Power BI Service
Gateway role tester
DAX security debugger

Correct answer: 'View as role' in Power BI Desktop or Service

'View as role' lets you preview the report as if you were a member of a specific RLS role, verifying that filters are applied correctly.

Question 26: How does refactoring a denormalized flat table into a star schema reduce Power BI memory usage?

It forces all dimension tables into DirectQuery mode
It replaces repeated text strings in the fact table with compact integer keys, improving compression (Correct answer)
It enables query folding on calculated columns
It removes all relationships, reducing model complexity

Correct answer: It replaces repeated text strings in the fact table with compact integer keys, improving compression

Integer foreign keys in a fact table compress far better than repeated text values; the VertiPaq engine achieves much higher compression on integer columns with low cardinality.

Question 27: What does the Power BI Admin Portal allow tenant administrators to manage?

Individual report designs and DAX expressions
Tenant-wide settings, user permissions, audit logs, and feature controls (Correct answer)
Power BI Desktop installation on client machines
Gateway configuration for each dataset individually

Correct answer: Tenant-wide settings, user permissions, audit logs, and feature controls

The Admin Portal gives Power BI tenant admins control over organization-wide settings, including export controls, sharing policies, and audit logs.

Question 28: What is the purpose of the 'Unpivot Columns' transformation in Power Query?

Converts multiple columns into attribute-value row pairs (Correct answer)
Converts row data into column headers
Removes selected columns from a table
Transposes rows and columns

Correct answer: Converts multiple columns into attribute-value row pairs

Unpivot Columns rotates selected columns into rows, creating an attribute column and a value column for each combination.

Question 29: What is Microsoft Purview's role in Power BI governance?

Providing data cataloging, lineage tracking, and sensitivity classification for Power BI assets (Correct answer)
Managing Power BI gateway connections
Handling Power BI billing and licensing
Running Power BI refresh jobs

Correct answer: Providing data cataloging, lineage tracking, and sensitivity classification for Power BI assets

Microsoft Purview integrates with Power BI to catalog assets, track data lineage, and apply sensitivity labels for enterprise data governance.

Question 30: What is the purpose of 'sensitivity labels' in Power BI?

Adding visual color labels to charts
Labeling measures with business descriptions
Marking reports as draft or final
Classifying and protecting content based on data sensitivity using Microsoft Information Protection (Correct answer)

Correct answer: Classifying and protecting content based on data sensitivity using Microsoft Information Protection

Sensitivity labels classify Power BI content (reports, datasets) by data sensitivity level and can enforce protection like encryption when exported.

Microsoft 70-778: Analyzing and Visualizing Data with Microsoft Power BI

Exam 70-778 validates skills in consuming and transforming data using Power BI Desktop, modeling and visualizing data with DAX, and configuring dashboards, reports, and apps in the Power BI Service. It is part of the MCSA: BI Reporting certification.

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35 min

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70%

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