  A model is proposed to address issues on the precise background evaluation
due to the complex data structure defined by the delayed coincidence method,
which is widely used in reactor electron-antineutrino oscillation experiments.
In this model, the effects from the muon veto, uncorrelated random background,
coincident signal and background are all studied with the analytical solutions,
simplifying the estimation of the systematic uncertainties of signal efficiency
and accidental background rate determined by the unstable single rate. The
result of calculation is validated numerically with a number of simulation
studies and is also applied and validated in the recent Daya Bay
hydrogen-capture based oscillation measurement.
