- Negative results, those that show something doesn’t work or there is no danger, often don’t get a lot of publicity – even if knowing that information could be important;
- Lack of funding for unexciting project leads to reduced efforts by researchers to replicate or validate previous studies;
- When studies are not replicated and validated the strength or their results is questionable, and they are likely to be overturned;
- Small sample sizes are prone to yield weakly supported results;
- Even with a larger sample, a one-time study may produce a statistical fluke rather than a real scientific finding;
- Finally, a lot of charlatans on TV and the Internet describe themselves as scientists and use scientific-sounding jargon to make a sale.
By the way, the example comes from August 2015 showing the truth in the first bullet point above that studies showing no danger get far less publicity.