Car alarms and smoke alarms: the tradeoff between sensitivity and specificity

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).<p>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.<p>(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.)<p>Conclusion: every sounding of a car alarm should attract a substantial tax penalty.

&quot;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.&quot;<p>Actually, I think it&#x27;s because the potential consequences of ignoring a smoke alarm (vs a car alarm) are much more grave.

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.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Alarm_fatigue" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Alarm_fatigue</a>

I have _never_ heard a car alarm that wasn&#x27;t a false alarm. And living in a large city, I hear one almost every night.

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 &quot;two by two diagram&quot;. You can find the full text of my articles here: <a href="https:&#x2F;&#x2F;www.researchgate.net&#x2F;profile&#x2F;Kevin_Johnson40" rel="nofollow">https:&#x2F;&#x2F;www.researchgate.net&#x2F;profile&#x2F;Kevin_Johnson40</a> 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.

&gt; 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.<p>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.<p>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&#x27;m suspicious they may actually up the risk of a fire, as someone may abandon their cooking to avoid the noise.

Wow... I haven&#x27;t heard a car alarm go off in so long I haven&#x27;t even thought about them at all in a few decades now.<p>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.<p>I learned to drive a beater there so I didn&#x27;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&#x27;t worth it to me. It was really nice to not worry about it.