Always try to spade multiple things at the same time, if you are spading drop rate, why not try and figure out the chip range for that foe as well? You could even determine thing ssuch as base crit/fumble chance, or more advanced things like how to hit and dodge work against that foe.
Section 1: Item Drop Rates
There are two ways to spade item drop rates, the long way and the short way. I prefer the long way because I feel it too be more accurate, and it is vastly cheaper in terms of item costs. It takes a lot longer though.
What you will need: spreadsheet, time
The long way is essentially recording drop rates. Every single time you encounter and defeat an opponent, you increment a counter for that opponent. Every single time an item drops you increment a counter for that item from that enemy. See my pet project below if that does not make sense. To then import those numbers to the wiki, you go to the enemies page, and you edit in a line like this
where x is the item number used for the name and image, y is the total foe encounters for that foe, and z is the number of times the item was dropped. It will look like this:
5 ± 4.4
Simple. I would recommend having multiple alts do this, because in order to get the uncertainty (number after the plus/minus) below 1% one must encounter the foe thousands of times. This can easily mean spending 10000 turns in one area, depending on the number of possible adventures. Not for the faint at heart or those with ADD.
What you will need: As much +item as possible, math skills
This methodology works the opposite of the long way. Your goal here is to find the lowest amount of +item that ensures the item will still always drop. This requires the ability to fine tune your +item easily. The easiest way to do this is Pouch of Many Lost Things. The math is as follows:
observed drop rate= base drop rate *(1+SUM(+item effects))
So this means the lowest possible base drop rate that can be raised to 100% with current equipment is 40% for regular items, 35% for squid discs, 32% for base metals, and 38% for sugar items. Use the guess and check method. You guess a base drop rate, and put on enough + item to ensure a 100% drop. Run a few hundred turns. If you did not get a drop, reduce your +item, run a few hundred turns. If you did get a drop increase your +item. increment in this fashion until a 1% difference in +item (see pouch above) changes it from a no-drop situation to a drop situation. Use the above formula to figure out the base drop rate using the no drop situation and 100% observed drop rate.
Verb. sap.: Probability is a bitch. Dont run just 100 turns, run a few hundred. The RNG will screw you. This method requires a lot of iotm, if you are trying to get into spading, it will cost you a lot of money to get the optimal gear. A lot.
My Pet Project
Goal: get all spading drop rates <1% uncertainty.
Currently: City of Lost Robots
If you wish to help, message me in game (same username) and I will add you for editing. Please only do so if you can carefully spade.
Eventually this might expand into a mega spading spreadhseet for everything from effects to initiative, but currently it is drop rates, and base character stats.