I'm working on a statistics project and need guidance to help me learn.

i have a set of data for good bags with low value , high value ,mean and st dev and set of data for bad bags with low value , high value , mean and st dev both of the data are different and low value for bad data is 20 and high value for good data is 18 , how can I find probability that bad bags data won’t fall under 18? I’m trying to establish a limit for a recipe when the bag reaches the limit the bag should fail.