Microsoft Power BI Data Analyst Practice Question

The correct formula is CALCULATE(SUM('Sales'[SalesAmount]), SAMEPERIODLASTYEAR('Date'[Date])). Here's a breakdown of why:

• The SAMEPERIODLASTYEAR function returns a table of dates shifted one year back from the dates in the current filter context. When a visual is filtered to March 2025, this function returns all dates for March 2024.
• The CALCULATE function then evaluates the SUM('Sales'[SalesAmount]) expression using this new table of dates as its filter context, correctly calculating the sales for the same period in the previous year.

Incorrect Answer Explanations:

• CALCULATE(SUM('Sales'[SalesAmount]), PREVIOUSYEAR('Date'[Date])) is incorrect because the PREVIOUSYEAR function returns all the dates from the entire previous year, ignoring the specific period (like a month or quarter) in the current filter context. This would return the total sales for all of 2024, not just March 2024.
• SUM('Sales'[SalesAmount]) - CALCULATE(SUM('Sales'[SalesAmount]), SAMEPERIODLASTYEAR('Date'[Date])) is incorrect because it calculates the year-over-year change or variance in sales, not the sales total from the prior year period itself.
• TOTALYTD(SUM('Sales'[SalesAmount]), 'Date'[Date]) is incorrect because TOTALYTD calculates the cumulative sum from the beginning of the year to the current date (Year-To-Date), which is a different calculation than comparing to the same period in the previous year.