Distribution analysis (box plots) in Tableau - Cell-by-Cell Formula Trace

Sample Data

Sales amounts for 9 transactions used to analyze distribution with a box plot.

Cell	Value
A1	Sales
A2	200
A3	450
A4	300
A5	700
A6	150
A7	400
A8	600
A9	350
A10	500

Formula Trace

Calculate quartiles and whiskers for box plot: Q1, Median, Q3, Lower Whisker, Upper Whisker

Step 1: Sort Sales values: {150, 200, 300, 350, 400, 450, 500, 600, 700}

Step 2: Find Median (Q2): middle value of sorted list

Step 3: Find Q1: median of lower half {150, 200, 300, 350}

Step 4: Find Q3: median of upper half {450, 500, 600, 700}

Step 5: Calculate Interquartile Range (IQR): Q3 - Q1

Step 6: Calculate Lower Whisker: max(min value, Q1 - 1.5 * IQR)

Step 7: Calculate Upper Whisker: min(max value, Q3 + 1.5 * IQR)

Cell Reference Map

    A   
1 Sales 
2 200  
3 450  
4 300  
5 700  
6 150  
7 400  
8 600  
9 350  
10 500 

The formula uses all Sales values from A2 to A10 to calculate quartiles and whiskers.

Result

  Sales Distribution Box Plot Summary
-------------------------------------
Q1 (25th percentile): 250
Median (50th percentile): 400
Q3 (75th percentile): 550
Lower Whisker: 150
Upper Whisker: 700

This summary shows the key values used to draw the box plot representing the sales distribution.

Sheet Trace Quiz - 3 Questions

What is the median sales value in the dataset?

A 400

B 350

C 450

D 500

Key Result

Box plot calculation finds Q1, Median, Q3 from sorted data, then computes whiskers using 1.5*IQR rule.

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