Pedigrees found on Ancestry and other sites are not always correct. Any type of research found, whether on line or published, is just an accident waiting to happen. Perhaps the best way to think of someone's research is a story, a story that needs to be verified with your own eyes.
I recently sat down with a client and she showed me the information she had accumulated. She had sourced someone's research in her genealogy program and had taken the research as the ultimate correct source. I asked her if she had reviewed any of the other researchers sources and she said she hadn't. Together we pulled up the tree on Ancestry, it appeared to have been copied from another tree, that tree had no verifiable sources. She doubted her own research and had discounted it as incorrect for a silly belief that if it was on Ancestry it was true. True she was new to research but I really thought I had drilled it into her head that she needed to see the proof herself - well I think she gets it now.
I want to elaborate just a little more. If I see another researcher has sourced a death certificate, I would still obtain a copy of the certificate myself. Why? I need to verify that the researcher correctly interpreted the information.
Believe in yourself and the research you can verify.