Thread 16774345

How many of you can correctly answer this?

>>16774345 (OP)
None of us, because the question doesn't list the false negative rate.

>>16774345 (OP)
Assuming 0% false negatives...
>1000 people, randomly sampled
>Test them all
>On average, 1 person in your sample actually has the disease, amogus
5% false positive rate means 0.05*999 healthy people test positive on average, or approx 50 false positives
So approx 50 false positives, 1 real positive
So approx 2% chance a given positive has the disease

If you assume it has 0% false negative rate, i think it's 2%
I dont believe that half of the people at harvard med think 95% of people have the disease

>>16774345 (OP)
True positive = 95%
False positive = 5%
20,000 people tested
2,000 actually have it
0.95*2000 = 1900 (true +)
0.05*18000 = 900 (false +)
1900/(1900+900) = 68%

>>16774345 (OP)
1/51 so a little less than 2%.

>>16774362
Correct except only 200 people actually have it kek

>>16774351
Thanks for telling us you've never been enrolled in an ivy league school.

>>16774366
correct except only 20 lol

>>16774362
who said there have been 20000 people tested

>>16774428
Very rude to say that, anon

>>16774468
How so?

>>16774495
Because you're implying someone is stupid. Very mean.

>>16774501
>I don't believe that half of harvard can't do basic math
It's not a dis, you've just never been there if you think that.

>>16774464
Easier to work worth

>>16774509
Idk, man. I think it's easier to assume 1000 people tested:
>1 person has it
>5% of 1000 = 50 false positives
>51 people test positive
>1 of them has it.
>1/51

>>16774517
The correct answer is 20/1019, not 1/51. The difference is that you've assumed the true positive rate is 100%, as opposed to being 95%. Assuming 20k people gets this answer. Yours doesn't.

>>16774518
>The difference is that you've assumed the true positive rate is 100%, as opposed to being 95%.
The question doesn't specify what the true positive rate is, anon. His guess is as good as yours.

>>16774518
>The difference is that you've assumed the true positive rate is 100%, as opposed to being 95%
I am retarded and do not understand what you're communicating here.
At 20,000 should the number of true positives not be 20? Should the number of false positives not be 1020?

>>16774518
the true positive rate is 1/1000 anon
it's literally stated in the problem

true positive = 1/1000
false positive = 50/999 (50 / 1000 for simplicity)

therefore true positive / false positive = 1/51
that anon is right

What does "false positive rate of 5%" mean? Does it mean a) 5% of the time the test says positive it's actually wrong or b) the test says 5% of the population has it?

>>16774576
It means "if you don't have the disease, there is a 5% chance the test returns positive anyway".

There is also the false negative rate: the chance that, if you do have the disease, the test returns negative. This rate is not listed in the question, which makes the question unanswerable.

>>16774585
If you remove iodine, hydrogen peroxide, latex gloves, and the confluence of how basic internal organs work together, the rest of medicine is no better than astrology.

>>16774609
Also splints. How to tie a bone down. Other than that, it's all horse shit.

>>16774612
Splints include tourniquets.

>>16774345 (OP)
nobody ever asks why a perfectly deterministic test would even have a false positive rate in the first place.

>>16774501
Everyone is stupid.
Stop pretending that remarks upon natural human cognition is an insult. Surely you're human and understand that you are frequently stupid.

>>16774708
People ask that all the time, it funnels into "p hacking"

>>16774708
What do you think these tests are? It's not some magic science machine that you stick some blood into and then "beep boop beep. You have diabetes."
There's tolerances of detection rate for various compounds within a sample. There's a magin for what's considered "normal." People outside that margin are sometimes perfectly healthy. People within that margin are sometimes horribly ill.
Biology be like that.

>>16774721
There were no remarks upon cognition, only upon experience.

>>16774728
It would be appreciated if you would cease demonstrating incompetence while whining about someone noting the presence of stupidity in populations of humans.
That you cannot see the way in which a remark upon experience with respect to cognition would be a remark upon cognition is a significant demerit.
The only person being insulted here is anyone forced to deal with you.

>>16774348
When they say <1/5 get it right, it means that FP+FN <= 0.2. The test given to the hypothetical patient is the same test given to the Harvard student is the same as OP's test. Radical semiotics can't wait to hear from you.
>>16774708
You just did.

tom bayes doing backflips in his grave

>>16774761
Tell me that in 8 words.

>>16774771
Shut the fuck up, dumb ass. People dumb.

>>16774783
The same balance of people go to harvard.

>>16774785
You literally said "Tell me that in 8 words."

>>16774828
Why did you break kayfabe by using 9?

>>16774835
>Why did you break my immersion by not continuing the bit you tacitly agreed to only once?
Ah, words.

>>16774840
Harvard peeps are largely daft. Try to disagree.

>>16774724
there shouldn’t ever be a margin if the test is designed correctly.

>>16774585
>tests just magically return positive for no reason other than pure chance
doctors are fucking DUMB

>>16775034
Nigger, have you ever had a real job in your life?
Protip: 1 and 1.0 are two very different numbers. 1.00 is another number entirely.
If you don't know why, then get a job.

>>16774362
So 5% false positive means 5% of people tested is wrongly diagnosed rather than 5% of diagnosed population is wrongly diagnosed. This just reinforces my conviction that all this logic questions is really just a gotcha questions that trap you with semantics rather than test actual reasoning skill. Nobody would fall for this if the definitions are properly spelt out.

>>16774345 (OP)
1/51?

>>16775073
It doesn't matter if you don't understand the question, "false positive" is a term doctors are familiar with, and the question was aimed at doctors

>>16774345 (OP)
Trick question the test is a ruse

>>16774345 (OP)
Think intuitively if the prevalence rate is 1/1000 nigga then 10/1000 is 1% of prevalence

>>16775206
Think nigga if your Iq isn’t the correct level then you’ll be retarded anything below 95 isn’t sentient imo aka the average women PhD

False positive rate is 5% that’s not relevant

False negative rate is 1% 1/1000 (prevalence) that’s all that matters so .1% of all false negatives cause death so 99.9% survival rate

>>16775220
I think my wm is back for intuitive reasoning not actual digit span which fucking sucks I’ll get it taken care of with the spells

>>16774348
Lmfao
>prevalence rate of .1%

>>16775220
Even I fucked up I used raw intuition still right tho I was initially close

>>16774501
Most people are stupid nigga

>>16774351
you used chatgpt retard
>i think muh 2
fucking faggot be decisive you have to use bayes theorum even me the all knowing anti memer got it wrong on the exact prevelance rate

>>16775288
probably some poojeet larping as intelligent lmao when in reality no poojeets are intelligent

I don't know these terms, but If I am understand this correctly:
>only 1 in 1000 people have the disease
>rate of occurrence 0.1% in the natural population
>a false positive rate of 5% means, that if you give it to a RANDOM person, they have a 5% chance to score positive on the test
>So if you gave the test to 1000 people, 51 people would score positive (the 5% false positives and the 0.1% of the population, who actually has it)
>So that's a 1 in 51 chance you are the person with the disease in purely mathematical terms
>that's like 1.9%

>>16776295
lmao great work cheating with my shit

>>16776590
I swear on my prostate, I didn't cheat.

Your stupidity is astounding.

>1/51
it amazes me that people keep quadrupling down on this wrong answer. just google the text of the question. there are dozens of sources with the correct answer online that you can verify none of which give as 1/51

>>16775207
>123test.com
>paying for an online IQ test
The score doesn't matter. You failed the real IQ test here.

>>16776295
>a false positive rate of 5% means, that if you give it to a RANDOM person, they have a 5% chance to score positive on the test
Almost. It means that if you give it to someone who doesn't have the disease, they have a 5% chance to score positive on the test. Which for this particular problem means almost the same thing, but not exactly.

>>16776295
>>So if you gave the test to 1000 people, 51 people would score positive (the 5% false positives and the 0.1% of the population, who actually has it)
Wrong. On expectation, the test would give you 50 positives from the false positives alone, but the true positive might be in that group too. There's a 19/20 chance that he's not. So instead of 50 people, you have 50 + 19/20, and the probability becomes 1 / (50 + 19/20) = 20/1019

>>16776620
>the true positive might be in that group too.
Then it's not a false positive now is it?

>>16776622
For the one truly sick person, there was still a 5 % chance that the test fails and gives a false positive. Or false false positive.

>>16776620
>On expectation, the test would give you 50 positives from the false positives alone, but the true positive might be in that group too.
This is a logically contradictory statement, if
>>16776615
>It means that if you give it to someone who doesn't have the disease, they have a 5% chance to score positive on the test.
is true.

I think you are wrong.

>>16776627
1/1000 chance that you have the disease and a positive result
5/100 * 999/1000 chance that you have a positive result but no disease
1/1000 + 5/100 * 999/1000 that there's a positive result
The chance that you have the disease is (1/1000)/(1/1000 + 5/100 * 999/1000) = 20/1019

>>16776624
We're talking mathematical idealism here. Any question regarding that actual workings of the test are to be ignored.
As such, it is not a false positive if it correctly flags a sick person as sick.

>>16776635
1/1000 chance you have it
50/1000 chance it's a false positive
total number of positives in 1000 is 50 + 1 = 51
only 1 of these is true
therefore 1/51

>>16774345 (OP)
Why weren't they taught how to perform the calculation? They're just supposed to infer the meaning of false positive rate as if they have a 180 IQ?

>>16776651
>50/1000 chance it's a false positive
Wrong. It's 5/100 that it's false positive, and 999/1000 that you don't have the disease. Please stop already.

>>16776656
>50/1000 =/= 5/100
Whatif it's 1/20?

>>16776656
nigga I literally have the book and this is the answer
try to reconsider

>>16776664
what book?

>>16776673
The book.
https://en.wikipedia.org/wiki/The_Book_(short_story)