My favorite folks over at The Consumerist posted a nice writeup on why ATMs do not have alarm buttons.
According to a FTC report, at about $1,500 a pop, they’re expensive to retrofit, the police usually don’t have the resources to respond in real-time, and they result in more false alarms than real calls. In one pilot program, an alarm-equipped ATM resulted in 500 false calls to the cops, and zero real robbery notifications.
For some human factors fun, try to calculate d-prime. 🙂
P.S. I don’t know how many instances of use there were total, so I can’t give a percentage on what percentage the 500 is.
why ATMs do not have alarm buttons? http://bit.ly/dlOF6A
Well, according to the grid, there were 500 uses of the alarm button in total, so 100% of uses were False alarms and 0% were hits. The non-uses of the button would be misses and correct rejections, no?
Fudging the numbers a bit so we can get z-scores:
z(.00000001) – z(.99999999) gives me about -11.2 for d’.
c is 9.1458E-10 by this estimate, so a slight bias to say that there is no alarm 😉
Of course that’s pretending there are no people who used the thing without pressing the button….