Versions of bad science
Bad Science often lacks objectivity. Misapplications of the tools of science to start with a preconceived belief and filter one's observations so as to try to support that belief. Scientists should be self-critical and try to disprove their hypotheses by all available means.
Bad science if often biased either by unrecognized preconceptions or by unreported personal affiliations and agendas. As mentioned above, good science often involves reductionism, but reductionism can fail.
Since good science strives to provide the simplest possible explanations of phenomena (Occam's razor), greedy reductionism is a common feature of bad science. Greedy reductionism is a derogatory label applied to failed efforts in reductionism where a it is incorrectly claimed that simple set of processes can account for or explain some other complex process or set of phenomena.
At the other extreme, bad science can result when it is assumed that the methods of reductionistic analysis will fail to explain certain phenomena, so attempts at reductionism and consilience are not even attempted.
Common forms of bad science
A common form of bad science is pseudoscience. Pseudoscience generally adopts the guise of science, but fails to utilise one or more of the required elements of good science such as skepticism. For example, creation science starts with a conclusion drawn from revelation and interprets data with the assumption that revelation cannot be wrong. Bad science is often unethical and offensive to social standards that apply to all human conduct.
Bad science judgements
Science can also be judged to be bad when it results in deleterious consequences. Some philosophers of science insist that science and scientists must take direct responsibility for regulating the search for knowledge and its practical applications. Science is widely judged to be bad when it is practiced and applied for selfish gain and without correction of deleterious side-effects.
See also