In the USA, we use traditional measures in everyday life, and SI when we have to communicate on topics that might have international interest, like science. One of the place that bleed over occurs is in medicine, which, although an art, subject to many individual vagaries, is allied to science.
Pediatrician, discussing fevers, said a low fever was 100.4 degrees Fahrenheit. I'd internalized the number as 100 years ago, and took a moment to see her thermometer: she had one set to report on the Celsius scale. 37 is 98.6, 38 is 100.4, 39 is 102.2, and 40 is 104 in the cute little lisp converter I wrote to figure this out:
(defun ftoc (x) ( * (- x 32) .5556)) ;Correctly translate Fahrenheit to Celsius (defun ctof (x) (+ ( * 1.8 x) 32)) ;Correctly translate Celsius to Fahrenheit
Result? I keep my definition, and note that the pediatrician may be using the Celsius numbers as shorthand for low, serious, and emergency fevers.
And add a new characteristic error to my collection. Do you have any favorite characteristic errors you notice?