I am teaching R since years. In a previous day lecture one of the participant asked a very important question. Since a lot of community members are contributing into R platform. What is criteria or system to check the package is performing consistently well. Means the results of functions are reliable. I know some of the policy related to package submission to CRAN. But I would specifically want to know is there any rating system for packages, how package results reliability is checked. Also we have packages that are provided in zip folders which are not part of the CRAN project. How can we ensure the confidence in using such packages?