The meme is talking about a common probability error that surveys have shown even doctors are prone to making.
Why you’re probably ok:
The rarity of the disease far exceeds the error rate of the positive test. Meaning, the disease occurs in 1 out of a million people, so if you are tested at random and show positive, you only have a 1 out of 30,000 chance (the 3% false-positive rate) of being the the 1 person who truly has the disease.
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Alright since I am actually currently learning about Bayes theorem. Assuming 97% accuracy means 3% chance of false negative and false positive. If you test positive. You have a 0.0032% of actually having the disease. If someone wants to double check me I encourage it.
Tactical RPGs have basically taught me that anything below 100% is almost always a miss and even 100% isn’t guaranteed.
I missed a very important 96% shot in XCOM last night. I’m still thinking about it.
The doctor is the one with the correct reaction there. Go do the second test.
I mean, yes…
But at 1/30,000 , they should say “get the second test… but be SUPER CAREFUL on the drive”, since at 1/30000 you’re still an order of magnitude more likely to die in an MVA.
This is ideal bedside manner.
I’ve always thought that I’d make an exceptional professional in the field of medicine.
The only thing really holding me back is my unfathomable depth of ignorance regarding the human body, or health in general.
At one point in my life, I believed that to be a deal breaker. Cheers, RFK Jr.
Accuracy and False Positive Rates are two different numbers.
I’m tired and my brain is being dumb right now, but when you said that my first thought was of course American. 97% accuracy grouping bullets is a lot different than 97% sure a gun was fired.
One says Johnny got shot in the kidney, the other says a truck may have misfired down the road.
This is one of the main reasons doctors don’t ‘just give you a battery of tests’. Not only is that expensive, but if you are running dozens of tests, the chance one of them gives a false positive is pretty high. So now you not only wasted a pile of money, but you also think you have some rare disease you don’t actually have. So you waste even more time and money treating that disease you don’t have.
Doctors run tests for things they think you might actually have, which diminishes the false positive chance.
Interpret it how you will.
This is why we use specificity and sensitivity stats for medical tests. If the test has a sensitivity of 97%, you should definitely be worried.
In the case of trying to minimize false positives, you want the specificity to be high, not necessarily the sensitivity, which is associated with false negatives.
And 97% specificity with a very low pretest probability still results in a low probability for disease, which is why screening for so many diseases is difficult, even if diagnosing them can be easy if there are clinical signs and symptoms in addition the the test. The clinical background can increase the pretest probability significantly, allowing the test to do its job.
Another very relevant video from 3Blue1Brown about the problem.
Yes, understood, ideally you would have two tests, one with high sensitivity to give some confidence that the disease is there, following by the high specificity test to compound the probability and rule out the false positive. Usually most tests have a trade off between specificity and sensitivity so two tests are needed.
Edit:
Watched the two videos, I love both these YouTubers but haven’t seen either video before. The calculating of the Bayes factor as an update to the prior odds was very interesting, helped increase my understanding, thank you.
I almost died of a dental abscess back in 2008, which led to a multi systemic failure. That was fun, but I’m still alive today.
Fuckall with worrying about life anymore, if I ain’t dead yet, well I’m not dead. I’m doing okay BTW…
Any day we’re all breathing is a good day
Be well, friend
Today I broke my personal record for consecutive days lived!
