I have just finished Lab exercise 2 questions, although I got correct answers but the questions are technically very wrong.
These are reference formula provided at the end of the exercise page.
"If you're stuck, check out the following DAX expressions to calculate similar measures, but on Units instead of Revenue."
Total Units = SUM(Sales[Units])
LY Total Units = CALCULATE([Total Units],SAMEPERIODLASTYEAR('Date'[Date])
Total Units Var = [Total Units] - [LY Total Units]
Total Units Var % = DIVIDE([Total Units Var],[LY Total Units])
POINTS TO NOTE:
Total sales = As per above formula (after changing units to revenue) It is the SUM of all sales, including ALL previous years from the beginning (year 1999). Please note that the current year(2015) sales figure is $136,959,026.68
Things are getting wrong from here:
LY Sales = The formula is actually asking to calculate revenue for the same period as in total sales i.e. from 1999 to 2015, DO WE HAVE DATA FOR THE CORRESPONDING PREVIOUS PERIODS OF 16 YEARS ? from 1980s something to 1998?? answer is No. So how can we calculate the same period number? but as per Power Bi defined answer it is all previous years except current year. Which is a completely incorrect way of thinking. The 2014 sales is 272,629,284.11
Total Sales variance is again making the same technical mistake of calculating sum of all previous years revenues to sum of all previous years revenue except current year.
Sales Var %, obviously if all numbers used in this formula are incorrect answer of the will be incorrect as well.
I would suggest Microsoft Power bi team to revisit the questions and correct it accordingly.
LY sales is all previous years up until 2014 , I was stuck in LY sales as well, I was using YTD Sales formula which was mentioned in the video, but then realised that the question is using
Total Sales = SUM(Sales[Revenue]) to calculate total sales . and
LY Sales = CALCULATE([Total Sales],SAMEPERIODLASTYEAR('Date'[Date]))
once you get these formulas right you will get the answer.