1. Add a Bar chart object onto the content page.
2. Add Month as a dimension.
3. Add Avg(Calls) as a measure. Label it Average Calls.
4. Click on Done. Notice that the values in both months are just below 150:

5. Next, go back into Edit mode and replace the measure with the following code:

Avg(If (Calls > Aggr(NODISTINCT Fractile(Calls, 0.1),
Month) and Calls < Aggr(NODISTINCT Fractile(Calls, 0.9),
Month),Calls))

6. Click on Done.

7. The chart should now resemble the following image. It not only has both bars significantly reduced, down to below 30, but there is also a much bigger gap between January's and February's average call volumes: