I’ve mentioned that the 30 percent figure shows a sampling bias?

Though if you wish to find more information on paternity fraud, simply google paternity fraud data, and things along those lines, doing so will give you all the info you need. The most famous study is from 2005:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1733152/

This covers many bases on the subject though it is a little outdated due to it being from 2005, but it provides a good beginning for research into the subject.

The Wikipedia page on the subject has got some great links at the bottom for further research as well:

https://en.wikipedia.org/wiki/Paternity_fraud#:~:text=A%202005%20scientific%20review%20of,30%25%20(median%203.7%25).

But again, simply googling the subject will provide you with the best information.

Hope this helps! Thanks again for reading :-)