Power BI calculations help

Hoping someone can help.....

I have a report that calculates measures of monthly means and std deviations on a ton of laboratory data (with date slicers). 

I then have some measures working off the mean and SD measures:

My report is broken down in to 3 rows,

i.e., i) Test,

ii) Lot no (193201/193203), and

instrument (C8000...).

What i really need to do is THEN caculate the SUM of "CV SQUARD MEASURE", i.e., for 193201 i want to sum up the total calculated values of all the instruments: 64.91 + 43.13 +20.61 +11.58 = 140.23 and NOT base it on the average of all the data, which is what is happening on the bold 193203 data line.

I have tried using SUMX:

Measure 2 = SUMX('FINAL IQC Summary', [SQRT CV SQUARE Measure]),

but when I try to put it in a visual, I get this:

 

 

I have tried to do a summarise table instead, but then I cant get visuals to dynamically change with a date slicer.

 

Any help appreciated for a complete novice!