We need your workbook to help, may be some with dummy data to see where u got stuck. and a VERY WARM WELCOME TO TABLEAU
Welcome to Tableau Community! Since you did not attach a workbook, I use superstore sample instead. In the screenshot, I made a set to identify all customer ID whose profit ratio (Sum(Profit)/SUM(Sales)) is >0.2. You can see I successfully highlighted all spots for profit ratio bigger than 0.2 with blue color.
Hope it helps.
Workbook attached (V10.2)
se.twbx 1.1 MB
Thank you both for taking time to help even without a dataset. I have attached a sample dataset that illustrates my issue.
For the sets i created (Cities with Low Margin Ratios) (Cities with Low Quick Ratios), applying a Color Mark card to the scatterplot doesn't reflect what I'm looking for, which is an imaginary straight line drawn vertically/horizontally down/across the graph splitting them into quadrants, with each quadrant signalling a margin/quick ratio of a certain group (for instance, less than 1.0, or less than 10).
The tutorial I used stated that it doesn't matter what Condition you apply to the set, because the tutorial data was "at the most granular level". Clearly, however, the condition matters in my case - when I select different conditions (SUM,COUNT,VARIANCE,etc.) the colored circles change, but none match my crtieria.
I hope I was more clear this time around in my explanation.