Overestimated stock market forecasts resulting from the one-time denoising
摘要
Accurate stock market forecasts are important for both investors and regulators. Prior research has argued the effectiveness of denoising-prediction models on stock market time series. However, the one-time denoising process may cause the in-sample series used for model training to be affected by the out-of-sample series, leading to overestimated accuracy. To test whether the denoising-prediction strategy contributes to improving stock market forecasts, this study introduces a sliding window to address the one-time denoising bias. The empirical mode decomposition (EMD) and variational mode decomposition (VMD) techniques are employed for denoising, and a non-iterative machine learning model, extreme learning machine (ELM), is employed as the predictor. Thus, a sliding denoising (SD)-EMD-ELM model and an SD-VMD-ELM model are developed. A comparison of the two models with individual and conventional denoising (D)-EMD-ELM and D-VMD-ELM models reveals that the superior performance of the denoising-prediction models is actually an overestimation due to the one-time denoising bias. This conclusion is corroborated by the technical implementation of the denoising process and the weak-form efficient market hypothesis.