Tableau-Desktop-Found Connecting to and Preparing Data Practice Question
Exhibit
{"error": "Calculation cannot be performed on mixed data types", "field": "Revenue", "current_format": "String", "expected_format": "Number"}Refer to the exhibit. You are receiving a calculation error when trying to aggregate a 'Revenue' field. What is the most efficient way to resolve this in the Data Source tab?
⚠ Common exam trap
Candidates often try to create a calculated field using functions like INT() or FLOAT() in the worksheet, missing the prompt's instruction to resolve the issue directly within the Data Source tab.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the data type of the field using the icon in the data grid.
Tableau requires numerical data to perform aggregate calculations like Sum or Average. If a field is imported as a string, it must be cast to a number. Understanding data type conversion is crucial because incorrect types prevent the use of fundamental features like filters and color-coding, which rely on the underlying mathematical properties of the data to generate accurate visual representations.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a new parameter to force numeric conversion.
Why it's wrong here
Parameters are user-input controls used to change values in formulas; they do not convert the data type of an existing field. Using a parameter for type casting is an inefficient workaround that does not solve the underlying issue of the data being incorrectly imported as a string.
- ✓
Change the data type of the field using the icon in the data grid.
Why this is correct
Clicking the data type icon at the top of the column in the Data Source tab allows you to convert the field to a 'Number (decimal)' or 'Number (whole)'. This is the standard, most efficient way to fix type issues immediately upon connecting to your data.
- ✗
Use a hide and unhide operation to refresh the schema.
Why it's wrong here
Hiding and unhiding fields only affects the visibility of the field in the workbook workspace. It has absolutely no effect on the data type or the internal metadata of the source data, meaning it will not resolve errors related to incompatible data types for mathematical operations.
- ✗
Export the data to CSV and re-import it.
Why it's wrong here
Exporting to CSV and re-importing is a destructive and time-consuming process. It does not guarantee the data type will be correctly inferred upon re-import, and it is entirely unnecessary given that Tableau provides built-in tools to change the metadata interpretation of any field directly within the software.
Visual reference
About these practice questions
One of 126 original Tableau-Desktop-Found practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Tableau (Salesforce) exam blueprint
This Tableau-Desktop-Found practice question is part of Courseiva's free Tableau (Salesforce) certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the Tableau-Desktop-Found exam.