Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Post History

50%
+0 −0
Q&A What's the average skill gain from successes in Call of Cthulhu?

Ignoring the extreme success case for now, and supposing the skill gives a probability p of success, then the probabilities of succeeding on the skill roll and then failing the learning roll (that ...

posted 1y ago by tommi‭  ·  edited 1y ago by tommi‭

Answer
#2: Post edited by user avatar tommi‭ · 2023-10-30T06:08:51Z (about 1 year ago)
  • Ignoring the extreme success case for now, and supposing the skill gives a probability p of success, then the probabilities of succeeding on the skill roll and then failing the learning roll (that is, getting the increase) is p(1-p). This is a parabel with top at 1/2 and zeros at 0 and 1. It is symmetric as all parabels are. (The function is a second degree polynomial with a negative highest order term.)
  • However, if you get to test the skill several times, say n times, then you have n chances to succeed, while you still only get a single test to confirm that you fail. I can calculate the probabilities if desired, but the main point is that lower skills are indeed favoured - any of the rolls succeeding gives the advancement chance, while there is only a single try at "failing" that one.
  • Ignoring the extreme success case for now, and supposing the skill gives a probability p of success, then the probabilities of succeeding on the skill roll and then failing the learning roll (that is, getting the increase) is p(1-p). This is a parabel with top at 1/2 and zeros at 0 and 1. It is symmetric as all parabels are. (The function is a second degree polynomial with a negative highest order term.)
  • However, if you get to test the skill several times, say n times, then you have n chances to succeed, while you still only get a single test to confirm that you fail. I can calculate the probabilities if desired, but the main point is that lower skills are indeed favoured - any of the rolls succeeding gives the advancement chance, while there is only a single try at "failing" that one.
  • The extreme success case happens rarely and essentially gives two attemps at the test to fail, so it will not affect the big picture, but it will somewhat improve the chances of success, especially where the skill level is high. A reasonable relative change, but still a small absolute one.
#1: Initial revision by user avatar tommi‭ · 2023-10-30T06:06:52Z (about 1 year ago)
Ignoring the extreme success case for now, and supposing the skill gives a probability p of success, then the probabilities of succeeding on the skill roll and then failing the learning roll (that is, getting the increase) is p(1-p). This is a parabel with top at 1/2 and zeros at 0 and 1. It is symmetric as all parabels are. (The function is a second degree polynomial with a negative highest order term.)

However, if you get to test the skill several times, say n times, then you have n chances to succeed, while you still only get a single test to confirm that you fail. I can calculate the probabilities if desired, but the main point is that lower skills are indeed favoured - any of the rolls succeeding gives the advancement chance, while there is only a single try at "failing" that one.