Ok, for the switch-on voltage of a red LED I have the readings as follows, all in volts: 1.45, 1.46, 1.46, 1.44, 1.45. The mean of these readings, in volts, is 1.45 (I rounded up to 2 decimal places as my scale reading uncertainty was +/-0.01V, and my teacher told me to round them up since to state my scale reading uncertainty for the mean the mean will have to have the same number of decimal places as the scale reading uncertainty). Now, my random uncertainty for these values is +/-0.004V, which is not to 2 decimal places (it's to 1 significant figure). So, I was wondering if I would have to make my random uncertainty have 3 significant figures (+/-0.00400V?) to express the random uncertainty in absolute form (Mean Value+/-Random Uncertainty). And if I did so, would it be, in terms of physics, correct?