Aluminum–magnesium alloys show the Portevin–Le Chatelier (PLC) effect. The aim of this publication is to provide a detailed analysis of the evaluation methods of this phenomenon using tensile tests at a strain rate range of 10⁻³ s⁻¹, where A and A + B stress serrations can be observed. Four smoothing and analytical functions are evaluated in detail as reference functions, which are compared based on their serration amplitude and frequency characteristics. The studied functions are the moving average and Savitzky–Golay smoothing method, as well as the Voce and polynomial analytic functions. The two smoothing methods and smoothing window sizes are compared to obtain the best reference function parameters.