Pie and donut charts in Power BI - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ visualization

intermediate

Choosing the best use case for a pie chart

Which scenario is the best fit for using a pie chart in a Power BI report?

A Displaying sales trends over multiple years for several products.

B Showing the percentage distribution of sales by product category for a single year.

C Comparing the total sales values of different regions using a bar chart.

D Listing detailed sales transactions with customer names and dates.

💡 Hint

Pie charts work best to show parts of a whole at one point in time.

Pie charts are ideal for showing how parts contribute to a whole, such as sales percentages by category in one year. Trends or detailed lists are better shown with other visuals.

❓ dax_lod_result

intermediate

Calculate percentage for pie chart slices

Given a Sales table with columns ProductCategory and SalesAmount, which DAX measure correctly calculates the percentage share of each category for a pie chart?

Power BI

Total Sales = SUM(Sales[SalesAmount])

A Category % = SUM(Sales[SalesAmount]) * 100

B Category % = SUM(Sales[SalesAmount]) / SUM(Sales[SalesAmount])

C Category % = DIVIDE(SUM(Sales[SalesAmount]), CALCULATE(SUM(Sales[SalesAmount]), ALL(Sales[ProductCategory])))

D Category % = CALCULATE(SUM(Sales[SalesAmount]), FILTER(Sales, Sales[ProductCategory] = EARLIER(Sales[ProductCategory])))

💡 Hint

Use DIVIDE and ALL to get total sales ignoring category filter.

Option C divides the sales for the current category by total sales across all categories, correctly calculating the percentage share for pie chart slices.

❓ data_modeling

advanced

Avoiding misleading pie chart slices

You have a pie chart showing sales by region. One region has very low sales, creating a tiny slice hard to see. What is the best data modeling or visualization approach to improve clarity?

A Group small regions into an 'Other' category using a calculated table or grouping feature.

B Remove the small region data from the dataset to simplify the chart.

C Change the pie chart to a donut chart without changing data.

D Increase the font size of the legend to make the small slice label more visible.

💡 Hint

Grouping small slices helps keep charts readable and meaningful.

Grouping small slices into 'Other' consolidates minor categories, making the chart easier to read and interpret without losing data.

🔧 Formula Fix

advanced

Fixing donut chart color mismatch

A donut chart in Power BI shows sales by product category, but the colors in the legend do not match the slices. Which option explains the cause?

A The measure used for values is not numeric, causing color mismatch.

B The data model has duplicate product category names causing color conflicts.

C The donut chart visual does not support legends, so colors are random.

D The chart uses a custom color palette that does not align with the data categories due to manual color assignments.

💡 Hint

Check if colors were manually assigned in the format pane.

Manually assigning colors to categories can cause mismatches if the order or categories change. Using consistent automatic colors avoids this issue.

🧠 Conceptual

expert

Limitations of pie and donut charts in BI dashboards

Which statement best describes a key limitation of pie and donut charts in business intelligence dashboards?

A They are ineffective for comparing many categories because small slices become hard to distinguish.

B They cannot display percentage values and require additional calculations.

C They always require 3D effects to be visually appealing and clear.

D They automatically update with real-time data without any configuration.

💡 Hint

Think about how many slices a pie chart can show clearly.

Pie and donut charts work best with few categories. Many small slices make it difficult to compare and interpret data accurately.

Practice

1. What is the main purpose of a pie chart in Power BI?

easy

A. To list data in rows and columns

B. To show parts of a whole as slices of a circle

C. To compare two numerical values side by side

D. To display trends over time with lines

Solution

1. Step 1: Understand pie chart basics

   A pie chart divides a circle into slices representing parts of a whole.

2. Step 2: Compare with other chart types

   Line charts show trends, bar charts compare values, tables list data. Only pie charts show parts of a whole as slices.

3. Final Answer:

   To show parts of a whole as slices of a circle -> Option B

4. Quick Check:

   Pie chart = parts of whole [OK]

Hint: Pie charts always show parts of a whole circle [OK]

Common Mistakes:

• Confusing pie charts with line charts
• Thinking pie charts show trends over time
• Using pie charts for detailed data tables

2. Which of the following is the correct way to add a donut chart in Power BI?

easy

A. Select the donut chart icon from the Visualizations pane

B. Write a DAX formula to create a donut chart

C. Use the Data view to draw a donut chart manually

D. Insert a pie chart and then change its color to white

Solution

1. Step 1: Identify how to add visuals in Power BI

   Power BI provides a Visualizations pane with icons for different charts.

2. Step 2: Find the donut chart icon

   The donut chart icon is available to select directly; no DAX or manual drawing is needed.

3. Final Answer:

   Select the donut chart icon from the Visualizations pane -> Option A

4. Quick Check:

   Donut chart = Visualizations pane icon [OK]

Hint: Use the Visualizations pane icons to add charts [OK]

Common Mistakes:

• Trying to create charts with DAX formulas
• Using Data view to draw charts manually
• Changing colors to fake chart types

3. Given a dataset with categories and sales, what will a donut chart show if you drag 'Category' to Legend and 'Sales' to Values?

medium

A. A bar chart comparing sales amounts

B. A line showing sales trend over categories

C. A table listing sales by category

D. Slices representing sales share of each category

Solution

1. Step 1: Understand donut chart data fields

   Legend defines slices (categories), Values define slice sizes (sales amounts).

2. Step 2: Interpret the visual output

   The donut chart will show slices sized by sales share per category, not trends or tables.

3. Final Answer:

   Slices representing sales share of each category -> Option D

4. Quick Check:

   Legend + Values = slices sized by values [OK]

Hint: Legend = slices, Values = slice size in pie/donut charts [OK]

Common Mistakes:

• Expecting a line or bar chart from a donut chart
• Confusing legend with axis in charts
• Thinking donut charts show raw numbers, not shares

4. You created a donut chart but it shows only one slice instead of multiple categories. What is the likely cause?

medium

A. The 'Category' field was not added to the Legend well

B. The 'Sales' field is empty or zero for all categories

C. The donut chart does not support multiple slices

D. The data model has no relationships

Solution

1. Step 1: Check the Legend field in the donut chart

   If 'Category' is missing or not properly added to Legend, the chart shows one slice.

2. Step 2: Verify other options

   Empty sales would show no slices, donut charts support multiple slices, and relationships affect filtering but not basic slices.

3. Final Answer:

   The 'Category' field was not added to the Legend well -> Option A

4. Quick Check:

   Legend missing = one slice [OK]

Hint: Always add categories to Legend for multiple slices [OK]

Common Mistakes:

• Assuming donut charts can't show multiple slices
• Ignoring the Legend field placement
• Blaming data model relationships for slice count

5. You want to show total sales in the center of a donut chart along with category slices. Which feature should you use in Power BI?

hard

A. Use the donut chart's center text option to display total sales

B. Enable the 'Detail labels' and set 'Label style' to 'Data value and percentage'

C. Add a card visual on top of the donut chart manually

D. Create a measure that sums sales and add it to Legend

Solution

1. Step 1: Understand donut chart limitations

   Built-in donut charts do not have a direct center text option for totals with multiple category slices; the center category label works only for single categories.

2. Step 2: Apply best practice workaround

   Create a total sales measure, add a Card visual to display it, and manually position the card in the donut's center hole. Other options fail: no center text (A), labels on slices (C), legend misuse (D).

3. Final Answer:

   Add a card visual on top of the donut chart manually -> Option C

4. Quick Check:

   Card overlay = donut center total [OK]

Hint: Overlay Card visual in donut center for totals [OK]

Common Mistakes:

• Believing donut charts have native center text for totals
• Adding totals to Legend field
• Using detail labels expecting center display