This strategy correctly implements a "what-if" analysis, which is the core of the client's request. A parameter allows the end-user to select a shipping vendor dynamically. A calculated field then references this parameter to perform a row-level calculation, determining the cost for each individual order based on the selected vendor's specific rates. Finally, Tableau aggregates these individual costs to display the total. This approach is highly performant because the complex calculation is only executed for the single, user-selected scenario, directly addressing the critical speed requirement.

A. This option avoids the technical challenge by changing the business requirements. It fails to provide a dashboard building strategy as requested.

B. Pre-calculating costs for every vendor for every order can create a very large and wide dataset, leading to slow query and load times, which violates the critical speed requirement.

C. Aggregating orders before applying the cost calculation is logically flawed. Shipping costs are typically determined per order based on its specific attributes (volume, speed), and this necessary detail would be lost through pre-aggregation.

1. Tableau Help

"Create Parameters"

Section: "Parameters in calculations". Official documentation states

"A common use for parameters is in calculations. You can reference the parameter in the calculation

and then you can show the parameter control in the view for users to select." This supports using a parameter for vendor selection to drive a calculation.

2. Tableau Help

"Swap Measures Using Parameters". This document provides a direct parallel to the required solution. While the example swaps measures like Sales and Profit

the principle is identical: using a parameter and a CASE statement within a calculated field to dynamically change the logic based on user input. The question requires swapping the cost calculation logic based on the selected vendor.

3. Tableau Help

"Use Parameters to Add More Interactivity to Your Views". This guide explains how parameters allow users to "input values into calculations to see how the data changes." This is the exact functionality needed for the client to model shipping costs by selecting different vendors. The document emphasizes this as a method for creating interactive

what-if scenarios.