Moreover, values of the propensity score near zero or one can lead to instability in the estimates as well as poor finite sample performance of the IPW estimator (Busso et al. 2013).
Following equation (2), the model was first estimated with the linear, squared and cubic coverage terms: ln C = a 0 + a 1 w + b 1 q + b 2 q 2 + b 3 q 3 + c 1 x 1 + c 2 x 2 + c 3 x 3 + c 4 x 4, The regressions with higher order terms in coverage were potentially collinear causing instability in the estimates.
A particularly disturbing feature is that for some types of problems there can be instability in the probability estimate as the location of the points is changed.
The EBS technique can be used to adjust for instability in the risk estimates caused by heterogeneity in the distribution of cases and the population.
There was a small amount of correlation (r = 0.55) between adjacent days, causing some instability in the PM2.5 estimates in an unconstrained distributed lag model.
Second, only about 1,000 women were diagnosed with IHD or pulmonary mortality, which may introduce some instability in the risk estimates.
(1995) that missing small events in the early stage of the aftershock sequence cause the instability of the estimate of the Omori Utsu formula.
Though there is some instability in the urinary cadmium effect estimates within age strata in the SDST analysis (learning recall/short-term memory), these results (Table 4) are consistent with interpretation that adjusting for age may result in the underestimation of the urinary cadmium-SDST association.
Some of the deficiencies related to the instability of the estimates in the classical SAVA approach can be overcome by using the Bayesian hierarchical models proposed within the disease mapping framework.
To ensure that the precision of the estimates was not affected by including the covariates listed above, we made sure that there were no signs of instability in the fitted model, such as unusually large estimates or standard errors.
