This paper addresses challenges in robust transfer learning stemming from ambiguity in Bayes classifiers and weak transferable signals between the target and source distribution. We introduce a novel quantity called the ''ambiguity level'' that measures the discrepancy between the target and source regression functions, propose a simple transfer learning procedure, and establish a general theorem that shows how this new quantity is related to the transferability of learning in terms of risk improvements. Our proposed ''Transfer Around Boundary'' (TAB) model, with a threshold balancing the performance of target and source data, is shown to be both efficient and robust, improving classification while avoiding negative transfer. Moreover, we demonstrate the effectiveness of the TAB model on non-parametric classification and logistic regression tasks, achieving upper bounds which are optimal up to logarithmic factors. Simulation studies lend further support to the effectiveness of TAB. We also provide simple approaches to bound the excess misclassification error without the need for specialized knowledge in transfer learning.

解决在稳健转移学习中由贝叶斯分类器的不确定性和目标与源分布之间弱可转移信号引起的挑战。我们介绍了一种称为''不确定性水平''的新量，用于衡量目标和源回归函数之间的差异，并提出了一种简单的转移学习过程。我们建立了一个一般定理，展示了这个新量与风险改进方面的学习可转移性是如何相关的。我们的提出的''Transfer Around Boundary''（TAB）模型，在平衡目标和源数据性能的阈值的基础上，既高效又稳健，在改进分类的同时避免了负转移。此外，我们还展示了TAB模型在非参数分类和逻辑回归任务上的有效性，达到了最优上限，与对数因子相匹配。模拟研究进一步支持了TAB的有效性。我们还提供了简单的方法来绑定过度的错误分类错误，无需在转移学习中专门的知识。

具有不可靠源数据的鲁棒传输学习