Science Often Isn't.

Study Finds: Studies Are Wrong - Hit & Run : Reason.com: "One of the bedrock assumptions of science is that for a study's results to be valid, other researchers should be able to reproduce the study and reach the same conclusions. The ability to successfully reproduce a study and find the same results is, as much as anything, how we know that its findings are true, rather than a one-off result...

That's why efforts like the Reproducibility Project, which attempted to retest findings from 100 studies in three top-tier psychology journals, are so important. As it turns out, findings from the majority of the studies the project attempted to redo could not be reproduced. The New York Times reports on the new study's findings: 

Now, a painstaking yearslong effort to reproduce 100 studies published in three leading psychology journals has found that more than half of the findings did not hold up when retested. The analysis was done by research psychologists, many of whom volunteered their time to double-check what they considered important work. Their conclusions, reported Thursday in the journal Science, have confirmed the worst fears of scientists who have long worried that the field needed a strong correction."