[eeZah7Ux]

This is computationally very heavy, but, more importantly, for practical purposes you want to have a tunable parameter to balance between sorting by pure rating average and sorting by pure popularity.

Often you also want to give a configurable advantage or handicap to new entries.

[quantdev]

For a fixed confidence level, it looks computationally light weight: a dozen or so multiplications and divisions plus one square root, which could be approximated if needed. There is no inverse normal needed at run time.