How Could I’ve Forgotten Uncertainty?

In the late afternoon, after closing the lid on some chicken that I had just started to BBQ, I decided to empty the compost bin. Since the next day was compost and recycling collection day, I figured that I might as well roll out both bins to the curb. Then my neighbor walked by with his dog, Edgar Allen Poe. We started to talk about trees on the street, flooding issues and eventually about how numerous and vocal the birds have been this spring and early summer.

My neighbor pointed out that his cat who died over the winter had been a major bird killer. But I doubted it was merely a local effect. Several people I know have been enjoying the new hyperactivity of birds recently . In addition, we’re not far from the city’s major airport. With the COVID-19 lockout earlier in the year, and with the ongoing and drastic reduction in flights, the neighborhood has been a lot more quiet, making the birds more audible, perhaps even encouraging them to sing a little more.

“Air traffic was especially heavy from about to 3 to 6 PM. I would notice plane after plane when I’d be BBQing….OH SHIT….Sorry, Charley. I just remembered I have BBQ going!”

I ran inside and back out through the patio door, hoping that my wife had come to the rescue. But she was busy preparing the vegetables. It had been 25 minutes. I was expecting to find carbon instead of breasts on the grill, at least on one side. But when I lifted the lid, the sides facing me were white and the flip side was beautifully streaked and deep- brown. But the flames seemed weak. I quickly flipped all four pieces and re-closed the lid.Within a minute I heard the popping last gasp of the empty propane tank.

How could the gas have run out in less than half an hour? Given that we have guests coming on Sunday, after the last time I used the BBQ, I weighed the tank. It was 20 pounds. With a tare weight of 17 lb, that meant I had 3 lb or about 3 hours left at its maximum setting. Then I remembered that scales have uncertainties. And the uncertainties for the bathroom scale I used are especially dependent on the weight being measured. Furthermore, it had been difficult to get a reading from directly placing the propane tank on the scale. So I weighed myself with and without holding the tank, which of course, doubles the uncertainty. You can see from this data that a 3 pound(1.4 kg) measurement could easily have been in reality 0.2 kg!

From, Accuracy and consistency of weights provided by home bathroom scales. BMC Public Health. 2013; 13: 1194

I can’t wait to run into my neighbor again to tell him what happened after I had panicked for nothing, merely because I had temporarily forgotten about the concept of uncertainty.

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