NPVn

NPVn is a notation commonly used in finance and statistics to indicate a version or time-indexed form of a more general measure. The most frequent interpretation is as the net present value calculated up to period n, often written NPVn or NPV_n, representing the sum of discounted cash flows from time 0 through time n. In this sense NPVn = Σ_{t=0}^n C_t/(1+r)^t, where C_t are cash flows and r is the discount rate. It can be used to track the cumulative value of a project as additional periods are considered.

In medical testing and diagnostic studies a subscripted form such as NPVn may be used informally to denote a negative predictive value calculated within a specific subgroup, time frame, or sample n; here NPV is the probability that subjects with a negative test truly do not have the condition. The subscript clarifies the context or sample to which the estimate applies.

Interpretation and use: NPVn helps assess the incremental contribution of additional periods, compare partial horizons, or perform sensitivity analyses. It is useful in staging investment appraisal, project monitoring, and subgroup reporting.

Limitations: As with any discounted-sum metric, results depend on assumptions about future cash flows and the discount rate; for diagnostic contexts, NPVn depends on prevalence and sample characteristics. Clear definition of the indexing convention is essential to avoid ambiguity.