Distribution analysis (box plots) in Tableau - Dashboard Guide

Dashboard Mode - Distribution analysis (box plots)

Business Question

How are sales distributed across different product categories? We want to see the spread, median, and outliers of sales amounts to understand variability and identify any unusual sales values.

Sample Data

Order ID	Product Category	Sales Amount
1001	Furniture	250
1002	Furniture	450
1003	Furniture	300
1004	Technology	1200
1005	Technology	1500
1006	Technology	1100
1007	Office Supplies	80
1008	Office Supplies	60
1009	Office Supplies	90

Dashboard Components

• KPI Card: Median Sales - Shows the median sales amount across all categories.
  Formula: MEDIAN([Sales Amount])
  Result: 300
• Box Plot Chart: Sales Distribution by Product Category - Visualizes minimum, first quartile (Q1), median, third quartile (Q3), maximum, and outliers for sales amounts per category.
  Tableau Setup: Drag Product Category to Columns, Sales Amount to Rows, and select Box-and-Whisker Plot from Show Me.
• Data Table: Sales Details - Lists all sales records with Order ID, Product Category, and Sales Amount for reference.

Dashboard Layout

+-----------------------+-------------------------+
|      Median Sales      |  Sales Distribution     |
|       (KPI Card)       |  by Product Category    |
|         300           |      (Box Plot Chart)    |
+-----------------------+-------------------------+
|                   Sales Details Table               |
|                  (All sales records)                |
+-----------------------------------------------------+
    

Interactivity

A filter for Product Category allows users to select one or more categories. When applied, the Median Sales KPI, Box Plot Chart, and Sales Details Table update to show data only for the selected categories. This helps focus on specific product groups and compare their sales distributions.

Self Check

If you add a filter to select only the Technology category, which components update and what changes occur?

• The Median Sales KPI updates to show the median sales amount for Technology only, which is 1200.
• The Box Plot Chart updates to display the sales distribution for Technology category only, showing its quartiles and any outliers.
• The Sales Details Table filters to show only sales records where Product Category is Technology.

Key Result

A dashboard showing sales distribution by product category using box plots, median sales KPI, and detailed sales data.

Practice

1. What does a box plot primarily show in data visualization?

easy

A. The total count of data points

B. The spread of data including median, quartiles, and outliers

C. Only the average value of the data

D. The correlation between two variables

Solution

1. Step 1: Understand box plot components

   A box plot displays the median, quartiles (Q1 and Q3), and any outliers in the data.

2. Step 2: Compare options to definition

   Only the spread of data including median, quartiles, and outliers correctly describes these features; others describe different charts or statistics.

3. Final Answer:

   The spread of data including median, quartiles, and outliers -> Option B

4. Quick Check:

   Box plot = median + quartiles + outliers [OK]

Hint: Box plots show data spread, not just averages [OK]

Common Mistakes:

• Confusing box plots with bar charts
• Thinking box plots show only averages
• Ignoring outliers in box plots

2. Which Tableau feature helps you quickly create a box plot?

easy

A. Using the 'Show Me' panel and selecting box plot

B. Writing a custom SQL query

C. Using the Data Interpreter tool

D. Applying a filter on the data source

Solution

1. Step 1: Identify Tableau tools for visualization

   Tableau's 'Show Me' panel offers quick chart types including box plots.

2. Step 2: Evaluate other options

   Custom SQL, Data Interpreter, and filters do not create visualizations directly.

3. Final Answer:

   Using the 'Show Me' panel and selecting box plot -> Option A

4. Quick Check:

   'Show Me' = quick box plot creation [OK]

Hint: Use 'Show Me' to pick box plot instantly [OK]

Common Mistakes:

• Confusing data preparation tools with visualization tools
• Trying to write SQL for box plots in Tableau
• Thinking filters create charts

3. Given a box plot in Tableau showing sales by region, what does the line inside the box represent?

medium

A. The average sales value

B. The maximum sales value

C. The median sales value

D. The total sales sum

Solution

1. Step 1: Recall box plot components

   The line inside the box is the median, which divides data into two equal halves.

2. Step 2: Differentiate median from average and extremes

   The average is the mean, not shown by the line; max is the whisker end; total sum is not shown.

3. Final Answer:

   The median sales value -> Option C

4. Quick Check:

   Box plot line = median [OK]

Hint: Median is the line inside the box, not average [OK]

Common Mistakes:

• Confusing median with average
• Thinking the line shows max or total
• Ignoring box plot whiskers

4. You created a box plot in Tableau but the whiskers are missing. What is the most likely cause?

medium

A. You forgot to add a measure to the Rows shelf

B. The data contains no outliers or extreme values

C. The data source is not connected

D. You applied a filter that removed all data

Solution

1. Step 1: Understand box plot requirements in Tableau

   Box plots need a measure on Rows or Columns to calculate quartiles and whiskers.

2. Step 2: Analyze each option

   No whiskers usually mean no measure is assigned; data connection or filters removing all data would prevent any plot.

3. Final Answer:

   You forgot to add a measure to the Rows shelf -> Option A

4. Quick Check:

   Missing whiskers = no measure assigned [OK]

Hint: Always add a measure to Rows or Columns for box plots [OK]

Common Mistakes:

• Assuming no whiskers means no outliers only
• Ignoring the need for measures in visualization
• Not checking data connection status

5. You want to compare sales distributions across multiple product categories using box plots in Tableau. Which approach best ensures clear comparison?

hard

A. Filter data to one category at a time and view box plots

B. Create separate worksheets for each category and compare manually

C. Use a pie chart to show sales proportions per category

D. Place product category on Columns and sales measure on Rows, then select box plot from 'Show Me'

Solution

1. Step 1: Set up box plot for multiple categories

   Placing product category on Columns and sales on Rows allows Tableau to create side-by-side box plots for comparison.

2. Step 2: Evaluate other options

   Separate worksheets or filtering one category at a time prevents direct visual comparison; pie charts do not show distribution.

3. Final Answer:

   Place product category on Columns and sales measure on Rows, then select box plot from 'Show Me' -> Option D

4. Quick Check:

   Side-by-side box plots = best for category comparison [OK]

Hint: Use Columns for categories and Rows for measure to compare box plots [OK]

Common Mistakes:

• Using pie charts instead of box plots for distribution
• Comparing categories in separate sheets
• Filtering to one category losing comparison context