Documentation standards in Power BI - Cheat Sheet & Quick Revision

Recall & Review

beginner

Why is documentation important in Power BI projects?

Documentation helps everyone understand the data, reports, and calculations. It makes it easier to maintain, update, and share the work with others.

beginner

What should a good Power BI documentation include?

A good documentation includes data sources, data model explanation, calculated measures, report purpose, and update instructions.

intermediate

How can you document calculated measures in Power BI?

Use clear names and add comments inside DAX formulas or keep a separate document explaining what each measure does and why.

intermediate

What is the benefit of using a data dictionary in Power BI documentation?

A data dictionary lists all tables and columns with descriptions. It helps users understand what each data element means.

beginner

Name one best practice for maintaining Power BI documentation.

Keep documentation updated whenever you change the report or data model to avoid confusion and errors.

What is the first thing to document in a Power BI report?

A Font sizes

B Color scheme

C User names

D Data sources

Documenting data sources is essential to understand where the data comes from.

Which of these is NOT typically part of Power BI documentation?

A User's personal preferences

B Calculated measures description

C Report refresh schedule

D Data model explanation

User's personal preferences are not part of standard documentation.

How can you add comments inside a DAX formula?

A /* comment */

B // comment

C # comment

D <!-- comment -->

DAX supports both /* comment */ and // comment for comments inside formulas.

Why keep documentation updated?

A To impress users

B To increase file size

C To avoid confusion and errors

D To slow down report performance

Updated documentation helps everyone understand the current state and reduces mistakes.

What is a data dictionary?

A A list of report users

B A list of tables and columns with descriptions

C A color palette

D A type of chart

A data dictionary explains the meaning of tables and columns in the data model.

Explain why documentation is important in Power BI and what key elements it should contain.

Think about how documentation helps others understand and use your report.

Describe best practices for maintaining Power BI documentation over time.

Consider what happens when reports change or new people use them.

Practice

1. Why is documentation important in Power BI reports?

easy

A. It hides data from users.

B. It increases the file size of the report.

C. It makes reports easier to understand and maintain.

D. It automatically fixes errors in data.

Solution

1. Step 1: Understand the purpose of documentation

   Documentation helps explain what the report does and how it works.

2. Step 2: Identify the benefit in Power BI context

   Clear documentation makes reports easier to use and maintain by others or yourself later.

3. Final Answer:

   It makes reports easier to understand and maintain. -> Option C

4. Quick Check:

   Documentation improves clarity = A [OK]

Hint: Documentation = easier understanding and maintenance [OK]

Common Mistakes:

• Thinking documentation changes report size
• Believing documentation hides data
• Assuming documentation fixes errors automatically

2. Which of the following is the correct way to add a comment in a DAX formula in Power BI?

easy

A. # This is a comment

B. // This is a comment

C.

D. /* This is a comment */

Solution

1. Step 1: Recall DAX comment syntax

   DAX uses double slashes (//) for single-line comments.

2. Step 2: Compare options with DAX syntax

   Only // This is a comment uses // which is correct for DAX comments.

3. Final Answer:

   // This is a comment -> Option B

4. Quick Check:

   DAX comments start with // = B [OK]

Hint: DAX single-line comments start with // [OK]

Common Mistakes:

• Using # which is for other languages
• Using HTML style comments
• Using /* */ which is not valid in DAX

3. Given this DAX measure with a comment:

SalesAmount = SUM(Sales[Amount]) // Total sales amount

What will be the output of this measure in a report?

medium

A. The sum of sales amounts plus the comment text

B. The text 'Total sales amount'

C. An error because of the comment

D. The sum of all sales amounts

Solution

1. Step 1: Understand how comments affect DAX measures

   Comments are ignored by the DAX engine and do not affect calculation.

2. Step 2: Evaluate the measure logic

   The measure sums the Sales[Amount] column values, so output is total sales amount.

3. Final Answer:

   The sum of all sales amounts -> Option D

4. Quick Check:

   Comments ignored, measure sums values = A [OK]

Hint: Comments do not affect measure output [OK]

Common Mistakes:

• Thinking comments become output text
• Assuming comments cause errors
• Believing comments add to calculation

4. You wrote this DAX measure:

Profit = SUM(Sales[Revenue]) - SUM(Sales[Cost]) // Calculate profit

But Power BI shows an error. What is the likely cause?

medium

A. The column names might be misspelled or missing.

B. DAX does not support comments at the end of a line.

C. You cannot subtract two SUM functions in DAX.

D. The comment syntax is incorrect in DAX.

Solution

1. Step 1: Check comment syntax validity

   The comment syntax // is valid in DAX, so comments are not the cause.

2. Step 2: Consider common errors in measure formulas

   Errors often come from misspelled or missing column names in SUM functions.

3. Final Answer:

   The column names might be misspelled or missing. -> Option A

4. Quick Check:

   Check column names first for errors = D [OK]

Hint: Check column names first when measure errors occur [OK]

Common Mistakes:

• Blaming comment syntax for errors
• Thinking SUM subtraction is invalid
• Assuming comments can't be inline

5. You want to document a complex Power BI report for your team. Which combination of documentation practices is best?

hard

A. Use clear names for tables and columns, add comments in DAX, and write descriptions for visuals.

B. Only add comments in DAX formulas; names and descriptions are optional.

C. Use vague names but add many comments in visuals only.

D. Skip comments and rely on team meetings to explain the report.

Solution

1. Step 1: Identify good documentation practices

   Clear names, comments, and descriptions help everyone understand the report easily.

2. Step 2: Evaluate options for completeness

   Use clear names for tables and columns, add comments in DAX, and write descriptions for visuals. combines all good practices: naming, commenting, and describing visuals.

3. Final Answer:

   Use clear names for tables and columns, add comments in DAX, and write descriptions for visuals. -> Option A

4. Quick Check:

   Combine naming, comments, descriptions = C [OK]

Hint: Combine clear names, comments, and descriptions for best docs [OK]

Common Mistakes:

• Relying only on comments or only on names
• Using vague names that confuse users
• Skipping documentation and relying on meetings