@connermcd
As a doctor I'm so happy you're using your platform to get this information out. Let me tell you though... it gets way more complicated! Unfortunately prevalence estimates aren't always known and are constantly changing (especially in pandemics). Another thing to consider is the gold standard. If your test looks for breast cancer you can cut out the lump and look at it under a microscope. Some diseases aren't as easily clarified. For instance, since we don't have a highly accurate, easy test for pancreatic cancer we rely on imaging, demographics, blood markers, symptoms (or lack thereof) as multiple things that form a conglomerate test to increase our Bayes factor. Despite all these things we can't always get a great prediction on whether that scar in your bile duct is cancer or just a residual scar from pancreatitis you had 10 years ago. So we offer the patient a huge surgery to remove the head of their pancreas and duodenum only to find that it wasn't cancer. You can imagine the patient is happy it's not cancer but not so happy they don't have half their pancreas and have abdominal pain and maybe diabetes. Medicine is a tricky thing. Another tricky thing is operator error. Some tests depend on the skill of the lab tech, radiologist, or surgeon. The complexity of the human body and the uniqueness of each individual also plays a role. Your test may be false positive in a particular patient 100% of the time because they have some strange protein mutation. It's tough!
@kingbradley3402
This is actual gold content being uploaded for free. It's like I'm unlearning what I learnt in all my classes and seeing Maths in a whole new way. I was asked in an interview one concept that is often confused but makes sense in general. I spoke about Bayes' Theorem. And this has given me something more to talk about. Quite possibly the best educational channel on YouTube.
@Asdfgfdmn
I hope Grant read this 😇 I am an MD and Associate Professor of internal medicine. I teach medical students, residents, and fellows. I used to be a program director for a fellowship at a prestigious American university. This is a recurring lesson I teach. The example I usually use is the DNAJB9 kidney biopsy stain sensitivity and specificity for a disease called Fibrillary GN., and I do the exact walkthrough with my students. I never get bored when I see how surprised they are with the final conclusion. Which is, by the way, is: you can't use a test willy-nilly without considering the pre-probability (you are referring to it here as ”prior.” And I also tell my students that you can increase the prevalence of the disease is by applying it to the right population (signs and symptoms). I am thrilled that Grant validated this with this awesome video
@D4n21
Medical Student here, THIS IS GOLD. THANK YOU, this is going to help with my boards and future patients
@Jebusankel
I'm going to apply this to the world of dating. Everything I learn about a potential match updates my prior about our compatibility. I call this Bae's rule.
@KX36
As a scientist who does medical tests, I'm amazed that any of the doctors asked got the right answer. Every doctor I work with assumes tests are 100% accurate.
@egillandersson1780
As doctors, we use this every day, often without thinking about the mathematical foundations. Unfortunately, very few diagnostic tests ou exams are indeed both sensitive AND specific. So, if we think a diagnostic unlikely (based on prevalence, physical exam, previous tests, ...), we choose first the more sensitive test in order to exclude this diagnostic. On the contrary, if a diagnostic is very probable, we choose first a specific test to confirm. It is not always easy for technical exams, as we can often only choose between them (if there are several !), without changing their sensitivity and specificity. But for biological tests, we can adjust our cutting values to improve either sensitivity or specificity.
@DJNHmusic
As a young doctor, thank you so much. I understood the distinction between the different accuracy parameters and PPV beforehand, but this has fundamentally changed how I view testing. This is a very useful thing to understand as a medical professional.
@hjfreyer
This is the first presentation of Bayes' theorem that didn't leave me feeling both like it was trivial and like it was inscrutable magic.
@Osamahtahir
As a medical student who's done this exact thing in a FAR more complicated way, thank you! In medical terms, the post-test odds = pre-test odds (the prior) * the positive likelihood ratio (the Bayes factor) This is an essential video for any medical professional to watch and understand! I'll be sending this to my instructor because you did such a great job at explaining an otherwise very confusing topic.
@RasperHelpdesk
Certainly drives home the point of why running a test twice after getting a positive result is so important when possible.
@tejing2001
This perspective makes the 'update' concept so much cleaner. I've long believed that until something is utterly obvious to you, you still don't truly understand it. I just got much closer to understanding bayesian updating. I could already do it, and even explain it, but it wasn't the same. True understanding is precious. Thank you for what you do, and as always, I look forward to the next video.
@eyabs
Thank you so much for this video. This concept of updating odds is what finally got Bayes' Rule to finally click in my head. I've used it a million times at work and it always bothered me how I couldn't do these simple calculations without pen and paper.
@egegorgun3411
Hey Grant, I am a third semester bachelor's student in physics and I find your videos very intuitive and absolutely inspiring. I find it very hard to deal with spherical harmonics this semester and as they are algebraicly complex but easy to visualize I thought maybe you can make a video about it too. It would help me very much at least. I can imagine these videos take a lot of effort and so I appriciate it very much. Thank You.
@wernerviehhauser94
This topic always breaks the brains of my students. Every year. Every time. This IS pretty hard stuff to wrap your mind around.
@davidholle6569
what really helped me was not using words like "sensitivity" but instead "true positive"
@krishmaheshwari3477
One of the greatest educators on YouTube!
@obnubilacion.9516
You won me with the short of this video! I'm a psychology students whose knowledge in statistics is minimal but i needed someone that make me understand these topics. Amazing
@DennisMathgod
This is so much better than the Veritasium video on this topic. You went into so much more detail and presented it in a very clear, easy to understand way. Nice job!
@johnchessant3012