7 ms·

What if Shark attacks are so low, because people pay attention to the risk? Just like airplane travel is safe because of all the regulations, not just out of it

by npstr 10y ago

What if Shark attacks are so low, because people pay attention to the risk? Just like airplane travel is safe because of all the regulations, not just out of itself? And I dislike measuring the micromorts per population, it should be divided by those people actually going swimming/surfing, just like riding x miles with a motorcycle increases your risk of dying by y micromorts, going swimming for a hours should be increasing your mms by b.

2muchcoffeeman 10y ago
Can any statisticians comment why total population is taken into account when only a portion actually participates in said activities?
- ch4s3 10y ago
  I think it's so that you can more easily compare things apples to apples.
  - gwern 10y ago
    I think it's just hard to estimate. How many visits-to-the-beach go into that shark attack number? It'd be useful to know the per-visit risk for the same reason it'd be useful to know the per-mile risk for driving, but is harder to estimate: "It’s important to be aware, however, that being based on population-level data, the micromort is not a measure of your personal risk. For example, the risk calculation for fatal shark attacks is based on the average risk across the whole population. So it effectively estimates a risk based on the assumption that all Australians swim in the deep ocean a similar number of times per year. But if you live in Alice Springs, you would not expect your risk of being killed by a shark to be the same as for a surfer who lives on the coast. Similarly, if you only wade in water up to your knees and don’t swim in deep water, your personal risks would be different."
  - jpttsn 10y ago
    Which sort of amounts to treating oranges as apples in the case. I always find it super silly when people apply population data to themselves. There's always much better data to go on if you know a bit about the individual.
- ramblenode 10y ago
  As others have said, possibly to make very disparate events comparable across a population, like the risk of skydiving vs. a shark attack. Unfortunately, this results in an almost useless measure for any particular individual when the probability of being in a risk group is small. Here is a breakdown of the risk for a random person in the US dying from skydiving in 2012 [0]: (1 death / 100,000 jumps) x (3 million jumps / 350,000 jumpers) x (350,000 jumpers / 313 million people) The last two terms give us the prior P(jump) ~= 0.01 and the first is the conditional probability P(death | jump) ~= 0.0001. The non-skydiver's risk factor is, of course, zero while the skydiver's risk is about 100x greater than that of the average person (who doesn't actually exist). As you can see, the population measure isn't very informative for either group. [0] http://adventure.howstuffworks.com/skydiving8.htm http://adventure.howstuffworks.com/skydiving8.htm
- laughfactory 10y ago
  As a statistician once told me: "the odds of running into a grizzly bear are miniscule, but if you're the one who runs into it, they're 100%." So it's important to remember that when evaluating odds and probability. Many things are unlikely to occur, but they do occur to some. I realize this is only tangential to your question, but wanted to put it out there.
  - k__ 10y ago
    Fair enough. But wouldn't it make sense to group people who are risk aware together? Like 90% of a population will live risk free lifes, and only 10% have high risk. I mean, depending how risk friendly 10% of the population are, they could screw up the result and then it seems all people of that population are crazier than most of them really are...
- imh 10y ago
  Lots of answers about apples-to-applesness, and such, but from a very practical viewpoint, the "said activities" part of "participating in said activities" is hard to define and measure. Should you condition on swimming, swimming in the ocean, swimming in the ocean in california, swimming in the ocean in the Santa Cruz area, or swimming in the ocean at Año Nuevo (or even some part of that beach)? However you decide to break it down, do you even have that data? In stats, lots of questions begin and end with "do you have data on that?"
obstinate 10y ago
Pretty easy to divide through by how much time the average person spends in ocean water to get your hourly risk. If such a number could be found, anyway.
ysavir 10y ago
And it should also be remembered that not all beaches are created equal. Some might be more dangerous than others.
M_Grey 10y ago
Most shark attacks turn out to be attacks of people surfing, boogie-boarding, or otherwise making themselves look like seals or similar mammal from the shark's perspective. Your risk while surfing is much higher than the average swimmer, never mind the average beachgoer who doesn't spend much time in the water.
- geebee 10y ago
  yep, and as I mentioned above, what percentage of those surfers are actually regulars in sharky places? We're talking about a very small slice of the total surfing population.
geebee 10y ago
The shark one is misleading, I agree. Out here in California, most people never go more than ankle deep in the water if that. Those who do surf usually only do it occasionally, in very un-sharky places. How many people really surf regularly in sharky places like Ano Nuevo, Russian River Mouth, Bolinas, and so forth? My guess is that you should probably be dividing the number of shark attacks by something measurable in the thousands, not 36 million. Whatever that number is, it's still damn unlikely. But still, if you're in the habit of surfing in known shark feeding grounds while dead seals are floating around, I don't think shark attacks divided by the total population of California is a good reflection of your risk.
- xapata 10y ago
  There's a wonderful (and heartbreaking) essay, "The Median is not the Message" by Stephen Jay Gould about cancer survival statistics. It expresses some of those points beautifully. https://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0003ms https://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=...
- averagewall 10y ago
  If you know more information, you can always change your estimates. Even if you're a surfer in a "sharky" place, what percentage of those are there at the same time as a shark? What percentage of those are chased by a shark? Bitten by a shark? If you're not one of the few that actually get bitten, then you're safe from death.
- kls 10y ago
  Agreed as a spearfisher (and a spearfisher in a sharky place), I am well aware that an overwhelming majority of attacks happen to spearfishers or related activities (abalone divers). It is not uncommon for a freediver with some sort of food to have an encounter with a shark and most people that have been doing it for a while have several stories. It comes with the territory but those who do it accept the risks. If you factored out spearfishers, abalone divers and surfers the numbers would look drastically different. The reality is it is very, very rare for some random person in the water to experience an unprovoked attack.

by npstr 10y ago

2muchcoffeeman 10y ago

Can any statisticians comment why total population is taken into account when only a portion actually participates in said activities?

ch4s3 10y ago
I think it's so that you can more easily compare things apples to apples.
- gwern 10y ago
  I think it's just hard to estimate. How many visits-to-the-beach go into that shark attack number? It'd be useful to know the per-visit risk for the same reason it'd be useful to know the per-mile risk for driving, but is harder to estimate: "It’s important to be aware, however, that being based on population-level data, the micromort is not a measure of your personal risk. For example, the risk calculation for fatal shark attacks is based on the average risk across the whole population. So it effectively estimates a risk based on the assumption that all Australians swim in the deep ocean a similar number of times per year. But if you live in Alice Springs, you would not expect your risk of being killed by a shark to be the same as for a surfer who lives on the coast. Similarly, if you only wade in water up to your knees and don’t swim in deep water, your personal risks would be different."
- jpttsn 10y ago
  Which sort of amounts to treating oranges as apples in the case. I always find it super silly when people apply population data to themselves. There's always much better data to go on if you know a bit about the individual.
ramblenode 10y ago
As others have said, possibly to make very disparate events comparable across a population, like the risk of skydiving vs. a shark attack. Unfortunately, this results in an almost useless measure for any particular individual when the probability of being in a risk group is small. Here is a breakdown of the risk for a random person in the US dying from skydiving in 2012 [0]: (1 death / 100,000 jumps) x (3 million jumps / 350,000 jumpers) x (350,000 jumpers / 313 million people) The last two terms give us the prior P(jump) ~= 0.01 and the first is the conditional probability P(death | jump) ~= 0.0001. The non-skydiver's risk factor is, of course, zero while the skydiver's risk is about 100x greater than that of the average person (who doesn't actually exist). As you can see, the population measure isn't very informative for either group. [0] http://adventure.howstuffworks.com/skydiving8.htm http://adventure.howstuffworks.com/skydiving8.htm
laughfactory 10y ago
As a statistician once told me: "the odds of running into a grizzly bear are miniscule, but if you're the one who runs into it, they're 100%." So it's important to remember that when evaluating odds and probability. Many things are unlikely to occur, but they do occur to some. I realize this is only tangential to your question, but wanted to put it out there.
- k__ 10y ago
  Fair enough. But wouldn't it make sense to group people who are risk aware together? Like 90% of a population will live risk free lifes, and only 10% have high risk. I mean, depending how risk friendly 10% of the population are, they could screw up the result and then it seems all people of that population are crazier than most of them really are...
imh 10y ago
Lots of answers about apples-to-applesness, and such, but from a very practical viewpoint, the "said activities" part of "participating in said activities" is hard to define and measure. Should you condition on swimming, swimming in the ocean, swimming in the ocean in california, swimming in the ocean in the Santa Cruz area, or swimming in the ocean at Año Nuevo (or even some part of that beach)? However you decide to break it down, do you even have that data? In stats, lots of questions begin and end with "do you have data on that?"

obstinate 10y ago

Pretty easy to divide through by how much time the average person spends in ocean water to get your hourly risk. If such a number could be found, anyway.

ysavir 10y ago

And it should also be remembered that not all beaches are created equal. Some might be more dangerous than others.

M_Grey 10y ago

Most shark attacks turn out to be attacks of people surfing, boogie-boarding, or otherwise making themselves look like seals or similar mammal from the shark's perspective. Your risk while surfing is much higher than the average swimmer, never mind the average beachgoer who doesn't spend much time in the water.

geebee 10y ago
yep, and as I mentioned above, what percentage of those surfers are actually regulars in sharky places? We're talking about a very small slice of the total surfing population.

geebee 10y ago

The shark one is misleading, I agree. Out here in California, most people never go more than ankle deep in the water if that. Those who do surf usually only do it occasionally, in very un-sharky places. How many people really surf regularly in sharky places like Ano Nuevo, Russian River Mouth, Bolinas, and so forth? My guess is that you should probably be dividing the number of shark attacks by something measurable in the thousands, not 36 million. Whatever that number is, it's still damn unlikely. But still, if you're in the habit of surfing in known shark feeding grounds while dead seals are floating around, I don't think shark attacks divided by the total population of California is a good reflection of your risk.

xapata 10y ago
There's a wonderful (and heartbreaking) essay, "The Median is not the Message" by Stephen Jay Gould about cancer survival statistics. It expresses some of those points beautifully. https://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0003ms https://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=...
averagewall 10y ago
If you know more information, you can always change your estimates. Even if you're a surfer in a "sharky" place, what percentage of those are there at the same time as a shark? What percentage of those are chased by a shark? Bitten by a shark? If you're not one of the few that actually get bitten, then you're safe from death.
kls 10y ago
Agreed as a spearfisher (and a spearfisher in a sharky place), I am well aware that an overwhelming majority of attacks happen to spearfishers or related activities (abalone divers). It is not uncommon for a freediver with some sort of food to have an encounter with a shark and most people that have been doing it for a while have several stories. It comes with the territory but those who do it accept the risks. If you factored out spearfishers, abalone divers and surfers the numbers would look drastically different. The reality is it is very, very rare for some random person in the water to experience an unprovoked attack.