Common LOD use cases (customer first purchase, cohorts) in Tableau - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ dax_lod_result

intermediate

Calculate Customer First Purchase Date Using LOD Expression

You have a sales dataset with fields: CustomerID, OrderDate, and SalesAmount. Which Tableau LOD expression correctly calculates the first purchase date for each customer?

A { INCLUDE [CustomerID] : MAX([OrderDate]) }

B { FIXED [CustomerID] : MIN([OrderDate]) }

C { EXCLUDE [CustomerID] : MIN([OrderDate]) }

D MIN([OrderDate])

💡 Hint

Think about fixing the calculation at the customer level to get their earliest order date.

The FIXED LOD expression fixes the calculation at the CustomerID level and returns the minimum OrderDate, which is the first purchase date for each customer.

❓ visualization

intermediate

Best Visualization for Customer Cohort Analysis

You want to visualize customer retention by cohorts based on their first purchase month. Which visualization type is best suited for this purpose?

A Pie chart showing total sales by product category

B Bar chart showing total sales per region

C Line chart showing number of customers retained over months by cohort

D Scatter plot of sales amount vs. order count

💡 Hint

Cohort analysis tracks groups over time, so a time series visualization is best.

A line chart showing retention over time by cohort clearly shows how each group of customers behaves month by month.

❓ data_modeling

advanced

Designing Data Model for Cohort Analysis

You want to perform cohort analysis by customer first purchase month and track their monthly retention. Which data model design is best to support this in Tableau?

A A star schema with a customer dimension table and a fact sales table including OrderDate

B Separate tables for customers and orders without relationships

C A single fact table with CustomerID, OrderDate, and a calculated FirstPurchaseDate field

D Only an aggregated table with monthly sales totals

💡 Hint

Think about how to relate customer info with their orders efficiently.

A star schema with a customer dimension and fact sales table allows easy calculation of first purchase and cohort grouping.

🎯 Scenario

advanced

Using LOD to Calculate Cohort Retention Rate

You have a dataset with CustomerID, OrderDate, and SalesAmount. You want to calculate the retention rate for each monthly cohort (based on first purchase month) for subsequent months. Which approach using Tableau LOD expressions is correct?

A Use a simple SUM aggregation of sales amount by month

B Use INCLUDE LOD to calculate average sales per month without cohort grouping

C Use EXCLUDE LOD to remove customer dimension and sum sales by month

D Use FIXED LOD to get each customer's first purchase month, then count customers with orders in each month divided by cohort size

💡 Hint

Retention requires knowing the cohort and tracking customers over time.

FIXED LOD fixes the first purchase month per customer, enabling cohort grouping. Then counting customers active in each month divided by cohort size gives retention rate.

🔧 Formula Fix

expert

Identify the Error in This LOD Expression for First Purchase Date

You wrote this Tableau LOD expression to get the first purchase date per customer: { FIXED [CustomerID] : MIN(OrderDate) }. However, Tableau returns an error. What is the cause?

Tableau

{ FIXED [CustomerID] : MIN(OrderDate) }

A OrderDate is missing brackets and should be [OrderDate]

B FIXED LOD cannot use MIN aggregation

C CustomerID should be aggregated inside the expression

D The expression must use INCLUDE instead of FIXED

💡 Hint

Check the syntax for field references in Tableau LOD expressions.

In Tableau, field names must be enclosed in square brackets inside LOD expressions. Missing brackets cause syntax errors.