✅ Step 1: Data Cleanup
Before analysis, make sure to clean the data as per instructions:

Exclude records where:

Quantity < 1 → These are returns or errors.

UnitPrice < 0 → Incorrect input, must be removed.

In Power BI (Power Query Editor):
Open the Power Query Editor

Apply filters:

Filter out rows where Quantity < 1

Filter out rows where UnitPrice < 0

Click Close & Apply

In Tableau (Data Source tab):
Use a calculated field or filter:

IF [Quantity] >= 1 AND [UnitPrice] >= 0 THEN TRUE ELSE FALSE

Filter only TRUE values.