How Many Cars Have Old Antennas?


How many cars have those long old school antennas (OSA)? You know, those long antennas, not the little knubs or "shark fin" types of modern antennas. Note that by "car" I really mean "automobile". Here is an example of the type of antenna I am referring to

I wrote the following interactive program for my calculator that keeps track of a (the event, in this case, if I see a car with an old school antenna), n (if any car is observed), and a/n (the number of cars with old school antennas divided by the number of cars), and does this by me just pressing two buttons, an ENTER key and a "(-)" key:

Lbl a
While k=0
If k=13:n+1->n
If k=13:0->ta[n]
If k=173:a+1->a
If k=173:n+1->n
If k=173:1->ta[n]
Disp "n: "&string(n)
Disp "a: "&string(a)
Disp "a/n: ",approx(a/n)
Goto a

This way I could just carry the calculator casually around at my side and press the keys without anyone knowing what I was doing. I also stored the vector of a's that I called "ta". I could then calculate a/n = sum(ta)/dim(ta) = mean(ta) at any time, not just see it on the screen at the time of the trial. I called this program "transect" because I plan to use it, or a modification of it, for various fun transect sampling work I am thinking about doing.

A total of 4 trials were carried out, each on a different level of a parking structure over two days. I figured that this way I'd be sure to get a reasonably fair mix of cars. I also measured my distance walked using the distance measurement tool on Google Maps. Note that each of the 1,117ft represents one lap around a floor of a parking structure. The work overall (programming plus walking) took less than 1hr.

Here are the results from the 4 trials:

  1. 6/18/18, Distance (ft): 1,117, OSA: 5, Total Cars: 65, OSA/Cars = ~7.7%, OSA/Distance = ~<.01/ft
  2. 6/18/18, Distance (ft): 1,117, OSA: 11, Total Cars: 130, OSA/Cars = ~8.5%, OSA/Distance = ~.01/ft
  3. 6/19/18, Distance (ft): 1,117, OSA: 12, Total Cars: 178, OSA/Cars = ~6.7%, OSA/Distance = ~.01/ft
  4. 6/19/18, Distance (ft): 1,117, OSA: 12, Total Cars: 171, OSA/Cars = ~7.0%, OSA/Distance = ~.01/ft
Combining all my trials, about 7% (=40/544) of cars have an old school antenna. I estimate my total distance walked to be 4,708 feet, which gives about .01 such antennas per feet walked in a parking lot, or about 45 per mile walked.

Here are some questions/comments I have. First, I expect the percent of cars that have an old school antenna to decrease to ~0% over time. The 7% number was actually much higher than I thought it would be. Second, I'd like to do trials, and many more of them, in really big parking lots, like in packed mega-store parking lots for example. Third, an old self-defense chestnut is that 'oh you can just rip off a car antenna to defend yourself'. Despite it probably taking a long time to bend the metal back and forth until it breaks (and seconds are infinity during a self defense situation), I showed even the frequency of such an encounter is too small to rely on. Last, as I mentioned already, I plan to use a similar program for investigating other questions I have that can be explored by using very simple relative frequency techniques.

Thanks for reading.

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