\label{fig:varRpTrapz} Relative uncertainties of the trapezoidal transit parameters derived from Kepler long-cadence data, as a function of \(R_p/R_\star\). The fiducial planet and star properties assumed are: \(R_\star = R_{\odot}\), \(M_\star = M_{\odot}\), \(e = 0.16\), \(P_{orb}=9.55~\rm{days}\), and \(b=0.2\). The solid red line gives \(R_p/R_\star\), corresponding to the analytic predictions from \citet{CarterEt2008ApJ} (their Equation 20), the dashed red curve gives the analytic predictions from \citet{CarterEt2008ApJ} including a finite-cadence correction (their Equation 26), and the solid black curve presents the analytic predictions accounting for a finite exposure time from this work (Equations \ref{eqn:cov1} and \ref{eqn:cov2}). The uncertainties derived from an MCMC analysis of simulated long-cadence Kepler data (blue crosses) agree well with the predictions of this work; we plot the measured uncertainty scaled by the true value of the parameter (where appropriate), so this plot does not reflect any systematic error in parameter measurement.