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Many challenges are now listed as 'Broad'. This means the probability of success increases linearly from 0 and up, with a roof on 100%. This is different from the previous system, 'Narrow', where the challenge only increased around +/- 5 levels from the challenge level.

The probability of success for a 'Broad' challenge relies on three things: the Level of the Attribute or Quality being tested, the Difficulty Level, and the Difficulty Scaler, as follows:

Probability of success = (Scaler) * (Quality Level) / (Difficulty Level). [rounded down]

Probability CalculatorEdit

 template = Template:Calculator/Probability
 form = Probability
 result = ProbabilityResult
 param = quality|Quality Level||int|0-350
 param = diff|Difficulty Level|50|int|1-1000
 param = scaler|Difficulty Scaler (%)|60|int|1-100
Calculator loading...

The difficulty scaler for Fallen London is 0.60 (as of 9th Sept. 2013). This gives the 'base' probability of success (60%), which occurs when the Quality Level equals the Difficulty Level.

The following adjectives are used to describe the difficulty of a particular challenge, based on the calculated probability:

  • 0-10%: almost impossible
  • 11-30%: high-risk
  • 31-40%: tough
  • 41-50%: very chancy
  • 51-60%: chancy
  • 61-70%: modest
  • 71-80%: very modest
  • 81-90%: low-risk
  • 91-100%: straightforward

e.g. a Broad challenge on Shadowy with a difficulty level of 50 would currently have the following chances of success:

  • 0-8: almost impossible
  • 9-25: high-risk
  • 26-33: tough
  • 34-41: very chancy
  • 42-50: chancy
  • 51-59: modest
  • 60-67: very modest
  • 68-75: low-risk
  • 76+: straightforward

The Beginner's Guide's section on Change Points has information about expected earnings of the challenge attribute (at least for main attributes) per attempt at the various difficulty levels, from 1.0 at “straightforward” to 4.2 at “almost impossible”.

For further reading, this Story Nexus reference describes this rather less drily.

More CalculatorsEdit

Difficulty LevelEdit

Work out the likely difficulty level, given your probability and quality level:

 template = Template:Calculator/Difficulty Level
 form = Difficulty
 result = DifficultyResult
 param = quality|Quality Level||int|0-999
 param = prob|Success Probability (%)|50|int|0-100
 param = scaler|Difficulty Scaler (%)|60|int|1-100
Calculator loading...

Relative ProbabilityEdit

Given your current probability of success, what quality level will you need to achieve your desired probability?

 template = Template:Calculator/Relative Probability
 form = RelProbability
 result = RelProbabilityResult
 param = quality|Quality Level||int|1-250
 param = prob|Success Probability (%)||int|1-100
 param = prob2|Desired Probability (%)|80|int|1-100
Calculator loading...

Challenge List GeneratorEdit

 template = Template:Calculator/ChallengeList
 form = ChallengeGenerator
 result = ChallengeGeneratorResult
 param = qualLink|Quality Link|Dangerous|string
 param = diff|Difficulty Level|50|int|1-1000
 param = scaler|Difficulty Scaler (%)|60|int|1-100
Calculator loading...