Challenge difficulty

2020-12-30T20:26:52Z

2458905: Correct 'forth' -> 'fourth'.

{{FIXME|reason=example not using findsPerDay}}

==What is it?==
For every [[Challenge checker]] in the system there is a ''Challenge difficulty'' calculated. The difficulty is based on on how many [[Geocacher]]s fulfill the challenge or not. Project-GC is running [[Challenge checker]]s in the background for tens of thousands of [[Geocacher]]s, this process is a part of the [[Auto-challenge-checkers|Auto-Challenge-Checker System]]. The result of these runs is used to calculate the ''Challenge difficulty''.

==How is it calculated?==
Basically the ''Challenge difficulty'' tells us what proportion of [[Geocacher]]s fulfill a challenge or not. The rating is an integer between 0 and 100, but should not be confused with percent. First off it's important to understand that the automatic challenge checker runs aren't automatically executed on the average [[Geocacher]], but more likely on the more hardcore [[Geocacher]]s. It's primarily executed on [[Geocacher]]s with more finds, regular users of [[Project-GC]] and also [[Paid membership|paid members]] of the site.

Then the [[Geocacher]]s the checker has been run on is divided into three categories:
* Region - [[Geocacher]]s that are determined to live in the same '''region''' as the [[Challenge]] itself.
* Country - [[Geocacher]]s that are determined to live in the same '''country''' as the [[Challenge]] itself, but not in the same region.
* World - All others

For each category a percentage of how many fulfill the [[Challenge]] is calculated. Then the results for each group is weighted different in the calculations, basically a list is created and the percentages are added into that list. A fourth factor is also added into the mix, the number of finds per day.

The number of finds per day isn't used as the raw number itself, but rather as '(1-($numFinds/$daysOld))*100'.

Then the difficulty is calculated as '$difficulty = (3*$worldPercent + 5*$countryPercent + 10*$regionPercent + $findsPerDay) / (3+5+10+1)'.

It should also be noted that there are usually more cached checker runs in the system from more local [[Geocacher]]s than from those living far away.

==Example==
* The Challenge is placed in Texas, United States.
* 80% of the [[Geocacher]]s in Texas fulfill it.
* 40% of the [[Geocacher]]s in the other states of the United States fulfill it.
* 30% of the [[Geocacher]]s in the rest of the world fulfill it.
* Then to weigh these differently using coefficients a sum is created like this: 3*80+5*40+10*30.
* This sum is then divided by 18 (3+5+10).
* The ''Challenge difficulty'' ends up being 740/18 = 41.11, which is rounded down to 41. The values are always rounded down to the closest integer.

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Challenge difficulty