Textbooks and online sources often say the industry standard for uncertainty is given at a confidence interval of 95 %. This means out of 100 measurements, 95 would achieve the specified value and deviate around this value in range of the +/- uncertainty given. For example temperature sensor: states uncertainty of 1 deg C within a certain range. So 95% of the time the uncertainty is within this range.
However i am not sure how this uncertainty is calculated. Is the uncertainty 2 times standard deviation or 2 times standard error?
If for example a temperature sensor says it measures temperature with an uncertainty of +/- 1 deg C, then did the manufacturer test this sensor say a thousand times at a controlled temperature, for example 25 C, calculated the mean to be 25 C of those 1000 measurements, and then give this uncertainty as +/- 2 times standard deviation/standard error to get the final uncertainty of +/- 1 deg C ?
Here is the source of the formulas and uncertainty explanantion: https://andyjconnelly.wordpress.com/2017/05/16/uncertainty-and-repeats/