Have you already tried doing this using Median(Aggr([Absolute deviation (days)]/[IDA estimated lead time (days)] , your dimensions))... here make sure that you are using the whole expression instead of the labels of your expressions?
Sunitha, did Sunny's post help you? If so, please be sure to click the Accept as Solution button on his post to give him credit. If you figured it out otherwise, please consider posting what you did for others. You can mark that as the solution at that point as well.
To help users find verified answers, please don't forget to mark a correct resolution or answer to your problem or question as correct.