Except, N-Gacha don't always have one R-card. The base for N-Gacha is 6xN. It's just that the probability for having one of those be R is too high to not have an R in there most of the time.

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Got this one about 5 minutes ago

And trends don't differ from normal statistics. They are most definitely not used as a base for calculations.
Trends are used when the data you are meassuring is of a highly mutable type, and thus won't allow you to build a test sample big enough for what you need (or make building such sample a very fast paced and expensive process) and then invalidate it in too short a time.

When such a thing happens, you build the best sample you can in your "non-mutable" lapse of time (the lapse of time the data won't shift so much it invalidates your previous data).
Onle then, you can apply/study trends, by repeating that sample building all over again, and analyzing how the two samples change lapse after lapse (and thus, finding out the way the changes might happen over time).

The whole scientific set of calculations for trends give you the tools to do similar calculations as base statistics on said shifting data. But they won't give you anything accurate if you didn't have any starting data, Just starting from 0 with trends will fail as much as using common statistics on shifting data