Therefore, limit your numeric expressions to the number of decimal places which are known to be valid. Suppose 10 volts is applied to a 3 ohm resistor. Don't enter numbers this way in your notebook. 3.33 amps might be appropriate. Use scientific notation where possible.
Units are part of every calculation and are treated mathematically the same as numbers.
In making unit conversions, or calculating calibration constants, for example, keep track of all units in the calculations. Suppose a tension transducer produces a 6.7 millivolt change in output in response to the loading of 2 grams on the transducer tip. In a subsequent experiment, suppose that the peak of a twitch is registered as a deflection of 197 millivolts. Here's a preposterous example in unit conversions. Some comments about notation in calculating averages, standard deviations, etc.