In this experiment you measure five unlabelled resistors the simplest way there is: read the voltage, read the current, divide. But with one voltmeter and one ammeter there are only two ways to wire the circuit, and neither of them gives the right answer — one always reads high, the other always reads low.
Why this experiment is different
The hidden error here is the instruments themselves. An ammeter is a small resistance added in series; a voltmeter is a large resistance placed in parallel that steals a little of the current. The moment you connect a meter, the circuit you are measuring is no longer the circuit that was there.
The three previous experiments showed three ways out: in viscosity by Stokes’ law the error was removed by theory, in momentum on an air track by symmetry, and in specific heat by calibration. None of them is available here: you do not know the meters’ resistances, and you have no standard resistor to calibrate against.
The fourth way out is this: make the same error twice, from opposite sides. When one wiring reads high and the other reads low, the truth is trapped between them. All that remains is to work out which wiring has the negligible error for which resistor — and that crossover sits exactly at √(RA·RV).
The Python section does something independent: instead of estimating from the two ends of the set, it fits all five resistors at once to pull both meter resistances out of the data. When two unrelated routes land on the same number, that number is no longer luck.