On 7/11/2016 5:51 PM, Chris Angelico wrote:
This is why it's important to be able to record precisions of arbitrary numbers. If I then measure the width of this corridor with a laser, I could get an extremely precise answer - say, 2,147 millimeters, with a precision of four significant digits, and excellent accuracy. But if I multiply those numbers together to establish the floor area of the corridor, the result does NOT have four significant figures. It would be 64 square meters (not 64.41), and the accuracy would be pretty low (effectively, the *in*accuracies of both measurements get combined). But on the other hand, if you want to know whether your new fridge will fit, you could measure it with the same laser and come up with a figure of 1,973 mm (four sig fig), which would mean your clearance is 174mm (four sig fig).
Wrong as to the last point. 2147 - 1973 = 174 has only 3 sig. figures. 2147 - 2144 = 3 has 1 significant figure. Subtraction of nearly equal numbers can cancel sig. figures.
> How do you
record this? Is it 174.0? 0174? "174 with four significant figures"?
None of these. -- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
