Comparing current month test result with previous

[Dhaii]

I have a table that has employees test result from 2016 and every month we add the result for that month. I want to show the difference in percentage of employees failed the latest month in the data set with the previous month. 
for example, the previous monthe percentage of failure was 0.50% and the current month is 1.15%. I want a card visual that shows "0.65%".

the table has these columns (employee ID, test date, test result(failed, passed)).

any way this could be achieved?

[ChielFaber]

I think the following Curbal video will give you the result your looking for:

https://youtu.be/-xBYtOVyMTs

This is a dax solution