After a particular selection you might have tree of max depth 10, but with the other selection you land on a tree of max depth 5, for example.
Personally, I've love to see a list of the conditions whose probabilities are increasing and decreasing with each selection. This may not be suitable for the average consumer, but it would be very educational! And also fun.
Ultimately, to your point, we learned that at times it can scare users more than it can help them (e.g., if a condition goes from 0.5% to 1%)... not to say that we can't do that above a certain threshold.
We'll keep testing this. Is there a certain minimum probability you'd want to see before seeing a condition (e.g., if something is 1% matching vs 10% vs 70%)?
If I were in charge of this project, I would strive for simplicity and for appeal to the widest audience, and not indulge the geeks, students, professionals, and hypochondriacs who might want this feature.
The casual user should get fuzzy names for probability values, as you already do. I wouldn't even let them see the numeric values - that seems like bad psychology and an invitation to ascribe the wrong meaning.
Maybe there is a way to make everyone happy though? Is there already a "debug mode" for developers? Making it possible (not easy, but possible) for users to activate debug mode might be a way to expose functionality which would provide the kind of information.
> Is there a certain minimum probability you'd want to see before seeing a condition (e.g., if something is 1% matching vs 10% vs 70%)?
For people like me, I'd like to be able to dynamically set the value myself.
For the general public - the way you do it now seems good.
As a geek with a few of my own "fringe interests" ;), I love this idea of making it so hacker types can see the adjusting rankings behind the hood.
Sometimes websites do this unintentionally by the things they leave in the html and what not, but would be fun to think of the easter eggs we could leave behind!
This is why, at this stage, we have a strong bias towards guiding people towards the right care provider rather than trying to replace them; it's more of an aid rather than substitute. One example of this is how some of our users have used the symptom tool with joint pain, and its helped them figure out that they should see a rheumatologist, who was then able to guide them towards the right care to treat their particular version of arthritis.
It's smart care providers like that that can really deal with the nuanced cases and make sure people minimize the risk that they miss things like a pulmonary embolism.