VOStat is a Web service providing interactive statistical analysis of astronomical tabular datasets. It is integrated into the suite of analysis and visualization tools associated with the international Virtual Observatory (VO) through the SAMP commu
nication system. A user supplies VOStat with a dataset extracted from the VO, or otherwise acquired, and chooses among $sim 60$ statistical functions. These include data transformations, plots and summaries, density estimation, one- and two-sample hypothesis tests, global and local regressions, multivariate analysis and clustering, spatial analysis, directional statistics, survival analysis (for censored data like upper limits), and time series analysis. The statistical operations are performed using the public domain {bf R} statistical software environment, including a small fraction of its $>4000$ {bf CRAN} add-on packages. The purpose of VOStat is to facilitate a wider range of statistical analyses than are commonly used in astronomy, and to promote use of more advanced methodology in {bf R} and {bf CRAN}.
A new approach called RESID is proposed in this paper for estimating reliability of a software allowing for imperfect debugging. Unlike earlier approaches based on counting number of bugs or modelling inter-failure time gaps, RESID focuses on the pro
bability of bugginess of different parts of a program buggy. This perspective allows an easy way to incorporate the structure of the software under test, as well as imperfect debugging. One main design objective behind RESID is ease of implementation in practical scenarios.
