In any of the aggregation functions in QS (Count, Sum, Max, etc.), you are able to define the scope of the aggregation with set analysis. Other powerful functions such as AGGR will help you define even more complex arrays of data.
The combination of functions makes QS very powerful. There are also other functions specific to a table that helps you move in a "window" for example: Above(), Below(), etc. which combined with the aggregation Count, etc. will give you the results you want
What exactly does this expression do in tableau? Maybe a little explanation so we could help? This could be achieved in different fashions; with the use of the classic if, else expressions or set expressions etc.. depends on the user's preference and the desired output.
And please note: everything you can do with Tableau can be done (much faster) with Qlik and NOT viseversa
In Tableau, the expression allows me to look at the entire dataset and for each person on the team, evaluate their % Correct (or Incorrect). The dataset is a compilation of tasks and each row has a person who did the task and whether they were correct or incorrect. I want to look at the data in its entirety to derive an overall %correct. I hope I'm explaining that well enough!
Sounds like I need to investigate the functions further!