In recent years, researchers have intensively investigated various topics in test-case prioritization, which aims to re-order test cases to increase the rate of fault detection during regression testing. The total and additional prioritization strategies, which prioritize based on total numbers of elements covered per test, and numbers of additional (not-yet-covered) elements covered per test, are two widely-adopted generic strategies used for such prioritization. This paper proposes a basic model and an extended model that unify the total strategy and the additional strategy. Our models yield a spectrum of generic strategies ranging between the total and additional strategies, depending on a parameter referred to as the p value. We also propose four heuristics to obtain differentiated p values for different methods under test. We performed an empirical study on 19 versions of four Java programs to explore our results. Our results demonstrate that wide ranges of strategies in our basic and extended models with uniform p values can significantly outperform both the total and additional strategies. In addition, our results also demonstrate that using differentiated p values for both the basic and extended models with method coverage can even outperform the additional strategy using statement coverage.