I am trying to calculate the lower limit for success rate with the following calculation
avg({Success Rate})- 3*(stdev({Success Rate}))

I am getting the following error: nesting of aggregrate functions is not allowed

The success rate is calculated using the formula below
count(ifelse(transactioncode = 14 OR transactioncode = 17, ‘Success’, NULL)) / count(transactioncode)

You can’t use the count function inside avg. That’s what nesting of aggregate functions mean (they’re both aggregate functions). To get around this, change your count function to countOver.

I think there’s also something wrong in your count function. If your condition is true (transactioncode = 14 OR transactioncode = 17), then you end up with count(‘Success’). Are you trying to count the number of occurrences of the string value ‘Success’? In what field? Is ‘Success’ a field or is it a string value?

Without seeing your dataset, I can’t tell what partition to use in the countOver. You have to replace Dimension in my calculated field by the appropriate field(s).