need math help for new program logic

[Mike Savvy]

hello!
I want to write a programm which check this symptoms to calculate the probability of corona- infection.

Symptom	%
Fever	87.9%
Dry cough	67.7%
Fatigue	38.1%
Sputum production	33.4%
...	...
Diarrhoea	03.7%
Haemoptysis	00.9%

How it would be correct to calculate it?
Thank you in advance!

[Mike Savvy]

Would such calculation be correct? I think not because if I have only fever and nothing other it means directly 88% what is not looks like truth

[Paul Clapham]

Is that supposed to mean "Probability of CV given Fever is 87.9%" and "Probability of CV given Fatigue is 38.1%"? Those are conditional probabilities, and there are rules for computing with those probabilities.

But you seem to be disputing the numbers themselves. Which is fine, "Garbage In, Garbage Out" as we say, but if you dispute them then there's no point calculating with them.

[Campbell Ritchie]

Mike Savvy wrote:Would such calculation be correct? I think not . . .

No. If 88% of people with Coronavirus have a fever, that doesn't mean that 88% of people with a fever have Coronavirus.

[salvin francis]

Campbell Ritchie wrote:... No. If 88% of people with Coronavirus have a fever, that doesn't mean that 88% of people with a fever have Coronavirus.

This falls under the fallacy: I love y therefore y loves me ;)

Also unrelated to the topic ... I'm kind of skeptical as how an excel sheet with a few binary fields can diagnose a disease. Personally, percentage is not a good metric to tell me if I have a disease or not.

[Paul Clapham]

Campbell Ritchie wrote:If 88% of people with Coronavirus have a fever, that doesn't mean that 88% of people with a fever have Coronavirus.

Exactly. And there's no math which will tell you what is the right number instead of 88%.

[Piet Souris]

Do you also want to answer questions like: this person has Fever AND is also coughing, what chance he has to have Corona's disease?

[Campbell Ritchie]

Paul Clapham wrote:. . . there's no math which will tell you what is the right number instead of 88%.

There might be such figures available, but if Coronavirus cases are multiplying, those percentages will change from day to day.