Length-of-stay times in hospital for COVID-19 patients using the smoothed Beran's estimator with bootstrap bandwidth selection

The survival function of length-of-stay in hospital ward and ICU for COVID-19 patients is studied in this paper. Flexible statistical methods are used to estimate this survival function given relevant covariates such as age, sex, obesity and chronic obstructive pulmonary disease (COPD). A doubly-smoothed Beran's estimator has been considered to this aim. The bootstrap method has been used to produce new smoothing parameter selectors and to construct confidence regions for the conditional survival function. Some simulation studies show the good performance of the proposed methods.