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How That 'Extra .9%' Could Ward Off a Zombie Apocalypse

netbuzz writes "The questioner on Quora asks: 'When is the difference between 99% accuracy and 99.9% accuracy very important?' And the most popular answer provided cites an example familiar to all of you: service level agreements. However, the most entertaining reply comes from a computer science and mathematics student at the University of Texas, Alex Suchman. Here's his answer: 'When it can stop a Zombie Apocalypse.'"

37 of 204 comments (clear)

  1. Statistics 101 by blackicye · · Score: 4, Interesting

    An example we were given in my Intro to Stats module once upon a time used the Space Shuttle Program.

    The numbers following the decimal point are very important when it might mean the difference between a Space Shuttle failing catastrophically instead of leaving / returning through the atmosphere intact.

    And the vast differences in manufacturing costs between a 99.9%, 99.99% and 99.999% fault tolerant component and why
    it would be necessary in the bigger picture of the complete system.

    1. Re:Statistics 101 by cusco · · Score: 3, Interesting

      I read once that one of the most important things to come out of the entire Apollo program was the concept of 'zero defect manufacturing', which until then had only been possible in small custom workshops.

      --
      "Think about how stupid the average person is. Now, realise that half of them are dumber than that." - George Carlin
    2. Re:Statistics 101 by girlinatrainingbra · · Score: 3, Insightful
      Yes, but the other key item is the incidence of "false positives" and "false negatives". Both of these incidences are very dependent upon the penetration of the disease in the general population in the first place. See the concept of sensitivity and specificity for more details.
      .
      But the summary is a test that is 99% accurate (for both true positives and true negatives) with the zombie incidence rate shown would have : the possibility that a positive test result being a true positive of only 1/6 = 16.66%

      whereas a test that is 99.9% accurate would have

      the possibility that a positive test result being a true positive of only 2/3 = 66.66%

      for the incidence of Zombies (Mad Human disease) given in that student's example.

    3. Re:Statistics 101 by Cryacin · · Score: 2

      Unfortunately 'zero defect manufacturing' was quickly negated by 'rubber stamp testing' and 'austeric quality manufacture'

      --
      Science advances one funeral at a time- Max Planck
    4. Re:Statistics 101 by sjames · · Score: 2

      Which meshed perfectly with the epidemic of management 9 envy. Er, Um, SURE, the stapler is five nines, six sigma, ISO 9000, and CORBA compliant.

    5. Re:Statistics 101 by Solandri · · Score: 4, Insightful

      Actually, the Challenger disaster hinged on a different failure in statistics. Originally the SRB segments were mated with 2 O-rings. Inspection of the SRBs after launch revealed the O-rings were failing at a higher than expected rate. So to mitigate the risk they redesigned the system and... added a 3rd O-ring. The reasoning was that if a single O-ring had a (say) 1% chance of failure, then two would have a .01^2 = .01% chance of failure, and three would have a .01^3 = .0001% chance of failure.

      Unfortunately, that reasoning only works when the failures are independent events. If a single event (like cold weather) can cause the failure of one O-ring, it can also cause the failure of the other O-rings, so that failure mode is not independent. And your chance of all three O-rings failing is closer to 1% instead of 0.0001%.

      Same thing happened at the Fukushima nuclear plant. They had something like a dozen diesel generators under the theory that even if a few failed to start, it was highly unlikely that all would fail to start. They completely missed the possibility that a single common event could cause all the generators to fail the same way.

    6. Re:Statistics 101 by stiggle · · Score: 2

      Which is why you'd make the O-rings out of different compounds, and install no set with all the same type.
      Locate the diesel generators in 2 or 3 power houses around the site.
      2+ server rooms on site with replication between them (with additional replication off-site).

      But how much resource do you throw at the problem? Its easy for us after the events to decide if NASA should have used O-rings of differing compounds or Fukashima have multiple power houses on different levels.

    7. Re:Statistics 101 by drinkypoo · · Score: 2

      Actually, the Challenger disaster hinged on a different failure in statistics.

      Yes, the specification sheet for the O-Rings stated that they would fail in those conditions 100% of the time...

      --
      "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
    8. Re:Statistics 101 by digitig · · Score: 4, Interesting

      Which is why you'd make the O-rings out of different compounds, and install no set with all the same type.

      Which still doesn't eliminate dependent failures, because the failure of one O-ring increases the stress on the next O-ring (particularly the burst of pressure as the first O-ring fails).

      Locate the diesel generators in 2 or 3 power houses around the site.

      Which doesn't eliminate dependent failures when the failures are due to a contaminated fuel delivery.

      2+ server rooms on site with replication between them (with additional replication off-site).

      Which doesn't eliminate dependent failures when the failures are due to common software running on all sites.

      But how much resource do you throw at the problem? Its easy for us after the events to decide if NASA should have used O-rings of differing compounds or Fukashima have multiple power houses on different levels.

      For that you could call me in. Working that out what I do for a living.

      --
      Quidnam Latine loqui modo coepi?
    9. Re:Statistics 101 by suutar · · Score: 4, Informative

      The key factor is that the trait being tested is rare; only one in 500 people has it. In this case, the false positives can still be (substantially) more frequent than true positives.

      Say you test 50,000 people. 100 have it, 49,900 don't. Of the 100 who have it, there will be 99 correct 'yes' results and one incorrect 'no' result. And of the 49900 who don't have it, there will be 49401 correct 'no' results and 499 incorrect 'yes' results.

      So total, we have 598 'yes' results. But 499 of those are false positives, which is 83.4444%; only 16.5555% of the folks who test positive are really positive.

  2. Re:That's not the question by Sussurros · · Score: 2, Interesting

    A zombie apocalypse happened in Britain and was shown in a BBC documentary by Derren Brown.

    --
    I said - don't look Ethel!..., but it was too late..., she'd already looked.
  3. You've got cancer! by complete+loony · · Score: 5, Funny

    A better answer; False positive medical tests.

    --
    09F91102 no, 455FE104 nope, F190A1E8 uh-uh, 7A5F8A09 that's not it, C87294CE no. Ah! 452F6E403CDF10714E41DFAA257D313F.
    1. Re:You've got cancer! by sapphire+wyvern · · Score: 2

      Actually, that's pretty much the context that the zombie plague answer is given in.

    2. Re:You've got cancer! by eennaarbrak · · Score: 2

      Spot on. I once spent some time (fruitlessly) trying to explain to a guy that a cheap test for HIV that has a false positive rate of 5% will be useful in sub-Saharan Africa (where the occurrence of HIV is around 10-20% of the population), but that very same test is useless in Scandinavia (where it will almost always report a false positive).

  4. Re:Shame on you Slashdot by Anonymous Coward · · Score: 2, Funny

    Don't link to a blogspam site that rips off the entire original article's content - link to the original site.

    Think of it as a tribute to Roland.

  5. Re:That's not the question by Cryacin · · Score: 5, Insightful

    Well aren't you the genius.

    The only difference between genius and insanity is that all the voices get along.

    --
    Science advances one funeral at a time- Max Planck
  6. Re:Just Let It Die by wonkey_monkey · · Score: 5, Insightful

    Just Let It Die

    I'm trying, but it just keeps coming back!

    This zombie fad is getting worn out. Just stop it, stop referencing it, stop producing zombie-related media, just STOP.

    Alternatively, you could stop trying to be the arbiter of what is good and worthy and just indulge in the media you do enjoy. I'm very sorry* if you feel marginalised by those who have an interest in all things undead and shambling, but no-one's actually forcing to watch The Walking Dead or Jersey Shore.

    *I'm not really

    --
    systemd is Roko's Basilisk.
  7. Re:That's not the question by Joce640k · · Score: 4, Funny

    Start by looking at yourself in a mirror. Maybe you'll see something whooshing over your head.

    --
    No sig today...
  8. Re:That's not the question by rioki · · Score: 2

    For example rabies. Sure the the infected are not "undead" but the world in 28 days later was not a fun place to be.

  9. Re:Morgan Freeman reading my obituary? by lxs · · Score: 2

    Morgan Freeman will outlive us all.
    God is immortal you know.

  10. Re:Invalid reasoning. by Xest · · Score: 2

    "A zombie apocalypse with disease spreading through the air is not even known fictional scenario."

    Isn't that how it works on The Walking Dead? Given that you turn into a zombie on that show if you die even if you were never bitten? That's the implication I took away from it - that it was an airborne disease that simply infects you and then turns you when you die.

  11. Poor judgement in TFA by GauteL · · Score: 2

    "You can't justify subjecting 5 people to the negative effects of the cure in order to save one zombie, so your discovery is completely useless."

    No. You would administer it and risk killing many healthy humans, because the alternative is certain annihilation of the human race.

    The premise of the story is fine though. Although my zombie analogy would be the difference between a 99% chance of no zombie outbreak in a year vs. a 99.9% chance. The former would mean a 37% chance of a zombie free century. The latter would mean a 37% chance of a zombie free millennium.

    1. Re:Poor judgement in TFA by Too+Much+Noise · · Score: 2

      Even poorer judgment, in fact, as his probability calculation relies on an actual rate of infection of 1 in 500. For such a highly contagious disease the rate of infection will grow (well, duh!) So if 1 in 500 gives about 83% false positives, when the infection rate reaches 1 in 50 the false positive chance drops to 33% and for 1 in 5 to 4%.

      So indeed 99% is quite good for a high contagion rate, not so good for low contagion and useless for something that's exceedingly rare (for a disease that affects only one person in 10000 a test that has a 99% detection rate will have 99% false positives)

  12. Re:That's not the question by tehcyder · · Score: 3, Insightful
    Just because people bite other people doesn't make them zombies. If they're not undead, they're not zombies.

    You can't write a story about a world where some weird virus makes people want to bite each other's necks and drink their blood and say it's about vampires. It's about a weird virus that makes people want to bite each other's necks and drink their blood.

    --
    To have a right to do a thing is not at all the same as to be right in doing it
  13. Re:That's not the question either by tehcyder · · Score: 5, Insightful

    It's probably of deep significance for cultural anthropologists where this zombie meme came from, but I'm actually sick&tired of the whole thing. Zombies == instant unfunny guarantee.

    What's worrying is not so much that there's a stupid meme, but that people can even begin to try to rationalise it and behave as though it could actually happen.

    Personally, I just think it's feeding the insane "survivalist" mentality that is spreading like a virus through the US. Oh, wait...

    --
    To have a right to do a thing is not at all the same as to be right in doing it
  14. Re:That's not the question by AK+Marc · · Score: 4, Funny

    Yeah, because if you don't follow Vampire Canon, the vampire FBI will hunt you down and turn you.

  15. Re:That's not the question by 91degrees · · Score: 2

    Zombie apocalypse is just the writer being cute. This applies to any potential pandemic.

  16. Re:That's not the question by Spy+Handler · · Score: 3, Interesting

    Ok they sound plausible. However in all such cases, the zombie apocalypse would be very short lived - the infected humans simply wouldn't be able to survive very long.

    There's a reason rabies didn't result in a rabies apocalypse...

  17. Re:That's not the question by goose-incarnated · · Score: 2

    Just because people bite other people doesn't make them zombies. If they're not undead, they're not zombies.

    You can't write a story about a world where some weird virus makes people want to bite each other's necks and drink their blood and say it's about vampires. It's about a weird virus that makes people want to bite each other's necks and drink their blood.

    So, basically, whether or not they behave like zombies is irrelevant, they have to be literally be killed and then reanimated? Leaving aside the levitating goalposts, I can still work with that (off of the top of my head) in a plot involving a defib or similar. Human bodies are remarkably easy to bring back to life as long as certain constraints are adhered to ... for example the countdown time limit before reanimation. So .. the viral infection -> hallucinations part of symptoms -> host infects others via biting -> symptoms only show themselves after heart stops -> heart restarted.

    No more goalpost moving - that's a realistic plot; adding constraints like "if they are reanimated then they are still not undead", or "The heart must stop and stay that way" is goal-post moving.

    --
    I'm a minority race. Save your vitriol for white people.
  18. Re:That's not the question by MaskedSlacker · · Score: 5, Insightful

    I wish such an agency existed. Then we wouldn't have that sparkling bullshit.

  19. Re:That's not the question by deimtee · · Score: 4, Informative

    It's not a virus, it's a parasitic protozoan that is common in cats.
    It's called toxoplasmosis gondii and it makes men violent and women horny.
    Rats also get it, and it makes them attracted to the smell of cat piss.

    --
    I'm guessing that wasn't on their radar screen...
  20. Brains by meta-monkey · · Score: 3, Funny

    I was with him until he said one of the perks of being the plague-stopping hero was having your biopic narrarated by Morgan Freeman, when I'd obviously much rather have Zombie Morgan Freeman doing the VoiceOver.

    "Brains. My, my, my, some sweet delicious brains would be mighty fine indeed. Brains."

    You know you just read that with Morgan Freeman's voice in your head.

    --
    We don't have a state-run media we have a media-run state.
  21. Re:Just Let It Die by TimHunter · · Score: 2, Funny

    Congratulations! You just won the Slashdot Sourpuss Prize. The award used to be a b.j. from the supermodel of your choice, but we realized you'd just think of something to gripe about it so we quit giving it out. Enjoy your fame.

  22. Re:That's not the question by ceoyoyo · · Score: 2

    Or any disease at all. What he's really pointed out is that you need to have an extremely specific test before you can even consider using it for screening. The textbook example is mammography.

  23. Re:That's not the question either by Sarten-X · · Score: 4, Interesting

    ...people can even begin to try to rationalise it and behave as though it could actually happen.

    It's also an educational opportunity. I occasionally do mentoring, and I've used zombies as a good example for a worst-case scenario for emergency preparedness. It provides a good narrative to cover a wide variety of situations where everything's gone wrong, without entering into a ridiculous movie-plot-specific series of impossibly unlikely events. By starting out with the assumption that we're already in a worst-case scenario, where the survivor is one of only a few to survive an epidemic, it's not a terribly large stretch to assume that the car won't start, or that there's a storm coming, or that an earthquake has broken gas lines, and the survivor can't rely on government services.

    Speaking of how impossible a zombie is, the zombie apocalypse also provides some ironically humane ways to discuss epidemiology, biology, medicine, and ethics, because pop-culture zombies are a convenient infection without suffering. The actual conversion process is rarely a focus in stories, and once the zombie is a zombie, they're too mindless to even fear harm. They just keep wandering, not even bothering to eat regularly... which brings us to discussing chemistry and thermodynamics.

    Personally, I just think it's feeding the insane "survivalist" mentality that is spreading like a virus through the US. Oh, wait...

    Jokes aside, we don't have any Communists or Nazis today to worry about, or Confederates, or British, or Spanish, or Visigoths, or Persians, or even rival tribes. We do have terrorists to fear, but there aren't any terrorists likely to launch a full occupation of the US. The survivalist mentality has always been here, but now we don't have any looming evil that we need to survive. While minor emergencies (such as those requiring the aforementioned preparedness) may happen, the barbarians aren't at the gate. They're in their living rooms, shouting insults into their XBox.

    --
    You do not have a moral or legal right to do absolutely anything you want.
  24. Re:That's not the question by Anubis+IV · · Score: 3, Informative

    It's worth noting that the the effects they cause on humans are small enough that they are only detectable when measured across large samples of people, and even then, only to a very small degree. The last time I saw a study on it, the impact was something like a 1-2% difference in reported moods/tendencies across a sample of, I believe, around 100 people, and while I think the report said it was statistically significant, even they admitted that for any particular individual it's nearly impossible that you'd notice any differences between their mood before and after an infection.

    Of course, the headline for the article where I first heard about the report was rather sensationalist in nature, and that's what everyone else picked up and ran with, rather than reading the actual findings from the report.

  25. Re:That's not the question by Artifakt · · Score: 2

    Granted freely, but the majority of those parasites occur in insect hosts. The only exception I can think of is a parasitic isopod that causes a host fish's tongue to atrophy and the isopod resides in that spot as it grows. The fish may just arguably have a psychological change - that is, it may think that what is occasionally touching the roof of its mouth is still just its normal tongue. I don't know offhand how you would prove or disprove that.
                As to whether a 'zombie' inducing parasite is far fetched in 'higher' species though, isn't there something seemingly very odd about the concept of a tiny creature with at most a very limited nural system, trying to get evolutionary advantages out of controlling something that is normally controlled by a human grade brain? That's still assuming the host isn't actually damaged much by whatever caused its death, and that the body hasn't taken further damage by post death processes before the parasite can take over. From your post, I'm visualizing a tiny worm-like parasite spread by bite, and weighing, say half an ounce. Then I'm imagining it developing a five ounce brain, just to be able to control basic bodily functions in a case where the host has, say, suffered a broken arm during the zombie apocalypse, so it's smart enough to keep that host body walking without that broken arm flopping around, turning itself into a compound fracture with protruding bone ends, and causing the host to rapidly bleed out.
              When you try to come up with a naturalistic mechanism that could allow zombies as they are seen in movies, you end up with a lot of unexplained parts. When you stick to what seems reasonable by real science, you end up with something I wouldn't call a zombie, i.e. a host that has vital signs, appears more as though it was a rabid animal, at worst, rather than undead, and that would still be subject to death from blood loss if you shot it somewhere else besides the head.

    --
    Who is John Cabal?