
Car alarms and smoke alarms: the tradeoff between sensitivity and specificity - r4um
https://blog.danslimmon.com/2012/11/02/car-alarms-and-smoke-alarms-the-tradeoff-between-sensitivity-and-specificity/
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bobince
The cost of a false alarm for a smoke alarm is borne by owner of the smoke
alarm. The cost of a false alarm for a car alarm is borne by everybody in
earshot (typically not the owner).

The car alarm owner is forcing an externality cost onto society; there is no
incentive for an individual car alarm owner to reduce false positives so it is
no surprise the products are so bad.

(Even in the true-positive case, the car alarm is extracting its value from
the attention of third parties to the thievery, at no cost to the owner.)

Conclusion: every sounding of a car alarm should attract a substantial tax
penalty.

~~~
dominotw
> every sounding of a car alarm should attract a substantial tax penalty.

I live in a poorer west side chicago neighborhood and car alarms go off all
the time. I am jolted out sleep frequently by multiple alarms going off at the
same time. I never experienced this in somewhat affluent neighborhoods, I
think poor ppl are more sensitive(no pun intended) to theft so they turn alarm
sensitivity all the way up.

So fining would affect poorer ppl more than rich ppl and might be politically
sensitive much like the chicago soda tax that was rolled back for this precise
reason.

~~~
smallnamespace
> So fining would affect poorer ppl more than rich ppl

Yeah but if you're getting woken up multiple times at night in a poor
neighborhood, then it's poor people who _don 't_ own car alarms who are
negatively affected the most.

~~~
dominotw
If you are poor you have much higher tolerance to things like these.

~~~
ctrl-j
If you are poor, you do not have a higher tolerance.

If you are poor, you have significantly less agency to effect change to remedy
your situation - so you have no choice but to tolerate things like these.

A rich person can move, install soundproofing, afford air conditioning to
sleep with the windows shut, etc...

A poor person can have interrupted sleep.

~~~
evincarofautumn
Yup, you have “higher tolerance” to things that have been continually forced
on you—doesn’t mean your tolerance is actually higher, just that you’re more
experienced at sucking it up.

I distinctly remember the day when I, as a young teenage boy, observed “Huh,
the girls in my class are a lot better than the boys at doing work they don’t
want to do. The boys complain and try to get out of it, the girls generally
just do it whether they like it or not.”

Then I realised—oh, the girls feel like they’re _expected_ to just do it. They
don’t feel as entitled to a say in the matter as the boys do, because that’s
how they’ve each been socialised.

And then I began seeing parallels everywhere…so that was the moment that set
me on the path of social activism, really.

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technotarek
"When a smoke alarm goes off in a school or an office building, everybody
stops what they’re doing and walks outside in an orderly fashion. Why? Because
when smoke alarms go off (and there’s no drill scheduled), it frequently means
there’s actual smoke somewhere."

Actually, I think it's because the potential consequences of ignoring a smoke
alarm (vs a car alarm) are much more grave.

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jdietrich
This phenomenon is a serious safety issue in hospital intensive care
facilities; with so many machines producing so many audible alerts, genuine
emergencies often go un-noticed.

[https://en.wikipedia.org/wiki/Alarm_fatigue](https://en.wikipedia.org/wiki/Alarm_fatigue)

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nikanj
I have _never_ heard a car alarm that wasn't a false alarm. And living in a
large city, I hear one almost every night.

~~~
mikestew
Worsened by the fact that you get an insurance discount if you have a car
alarm. So everyone has one, despite that we all know they are only effective
at annoying neighbors and bystanders. The only writing I've read that touts
the positives of a car alarm fall in the "wishful thinking" category, a.k.a,
"well, it can't hurt!" Everything else I've read that tried to be at least a
little scientific indicates they're more trouble than they're worth.

~~~
jonas21
On the other hand, it's possible that the reason car alarms are mostly false
alarms these days is due to the huge decline in auto theft rates over the last
30 years [1], which is due at least in part to the prevalence of car alarms.

[1]
[https://www.insurancejournal.com/news/east/2014/12/17/350442...](https://www.insurancejournal.com/news/east/2014/12/17/350442.htm)

~~~
mikestew
30 years ago I could open a locked car, and get it started and driveable in
sixty seconds (the steering wheel lock will be collateral damage). Not a car
thief, but I _was_ a mechanic. But now there are better door locks, a lot of
cars don't even _have_ a key-locked wheel lock, and you don't just short two
wires under the dash to start it like the movies. Granted, a career thief
probably has quick workarounds for all of this, but the bar for quick car
theft went up from "low-life with a slim jim", I think.

Point is, yeah, car alarms likely had some effect, but was it more or less
than the fact that cars are just generally harder to steal now? And I have no
idea what the answer is.

~~~
loeg
> you don't just short two wires under the dash to start it like the movies.

Just plug in your ODB-II tool and press start :-).

~~~
namibj
After pressing the FPGA-based keyfob. When not used for cracking keyfobs, it
can also do other misc work.

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fred_and_fred
I had to struggle with this concept as a physician trying to understand the
medical literature. Eventually I came up with my own way of thinking
dynamically about it. I called this the "two by two diagram". You can find the
full text of my articles here:
[https://www.researchgate.net/profile/Kevin_Johnson40](https://www.researchgate.net/profile/Kevin_Johnson40)
As a matter of fact, I would very much like to get this programmed into a
Javascript version I can make freely available to people, but am not clear on
how to go about getting that done. I have a version in MATLAB but that is not
practical for most people.

~~~
irickt
Visual Presentation of Statistical Concepts in Diagnostic Testing: The 2 × 2
Diagram, Kevin M. Johnson and Benjamin K. Johnson.

[https://www.researchgate.net/profile/Kevin_Johnson40/publica...](https://www.researchgate.net/profile/Kevin_Johnson40/publication/263322395_Visual_Presentation_of_Statistical_Concepts_in_Diagnostic_Testing_The_2_2_Diagram/links/54c108500cf21674cea1e249.pdf)

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nitwit005
> People trust smoke alarms. When a smoke alarm goes off in a school or an
> office building, everybody stops what they’re doing and walks outside in an
> orderly fashion.

No, it means someone was making popcorn. The reason we leave is because they
set the volume to a level that it causes people to feel pain, presumably to
force us to leave.

The fire alarm at my apartment is effectively a bacon detector. Multiple
residents have covered theirs because of how sensitive they are. Normal
cooking will set them off. I'm suspicious they may actually up the risk of a
fire, as someone may abandon their cooking to avoid the noise.

~~~
aaronmdjones
If you have a smoke alarm installed in your kitchen (or wash room if that's
separate) that is a problem. Kitchens need heat alarms instead for this exact
reason; smoke alarms are too sensitive and are likely to be set off by other
things (dust from linen, steam from a kettle, toaster, tumble-dryer, etc).

In the UK, new residential construction puts heat alarms in kitchens and smoke
alarms everywhere else.

EDIT: If you have a dedicated central heating boiler room, that also gets a
carbon monoxide alarm.

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oblib
Wow... I haven't heard a car alarm go off in so long I haven't even thought
about them at all in a few decades now.

No one uses them in the rural area I live but the title to this and a few of
the comments here reminded me of how annoying car alarms could be when I lived
in LA.

I learned to drive a beater there so I didn't have to worry about someone
banging into or stealing my car. I saw too many people get way too stressed
about that and it just wasn't worth it to me. It was really nice to not worry
about it.

