<P> The overall process involves making conjectures (hypotheses), deriving predictions from them as logical consequences, and then carrying out experiments based on those predictions to determine whether the original conjecture was correct . There are difficulties in a formulaic statement of method, however . Though the scientific method is often presented as a fixed sequence of steps, these actions are better considered as general principles . Not all steps take place in every scientific inquiry (nor to the same degree), and they are not always done in the same order . As noted by scientist and philosopher William Whewell (1794--1866), "invention, sagacity, (and) genius" are required at every step . </P> <P> The question can refer to the explanation of a specific observation, as in "Why is the sky blue?" but can also be open - ended, as in "How can I design a drug to cure this particular disease?" This stage frequently involves finding and evaluating evidence from previous experiments, personal scientific observations or assertions, as well as the work of other scientists . If the answer is already known, a different question that builds on the evidence can be posed . When applying the scientific method to research, determining a good question can be very difficult and it will affect the outcome of the investigation . </P> <P> A hypothesis is a conjecture, based on knowledge obtained while formulating the question, that may explain any given behavior . The hypothesis might be very specific; for example, Einstein's equivalence principle or Francis Crick's "DNA makes RNA makes protein", or it might be broad; for example, unknown species of life dwell in the unexplored depths of the oceans . A statistical hypothesis is a conjecture about a given statistical population . For example, the population might be people with a particular disease . The conjecture might be that a new drug will cure the disease in some of those people . Terms commonly associated with statistical hypotheses are null hypothesis and alternative hypothesis . A null hypothesis is the conjecture that the statistical hypothesis is false; for example, that the new drug does nothing and that any cure is caused by chance . Researchers normally want to show that the null hypothesis is false . The alternative hypothesis is the desired outcome, that the drug does better than chance . A final point: a scientific hypothesis must be falsifiable, meaning that one can identify a possible outcome of an experiment that conflicts with predictions deduced from the hypothesis; otherwise, it cannot be meaningfully tested . </P> <P> This step involves determining the logical consequences of the hypothesis . One or more predictions are then selected for further testing . The more unlikely that a prediction would be correct simply by coincidence, then the more convincing it would be if the prediction were fulfilled; evidence is also stronger if the answer to the prediction is not already known, due to the effects of hindsight bias (see also postdiction). Ideally, the prediction must also distinguish the hypothesis from likely alternatives; if two hypotheses make the same prediction, observing the prediction to be correct is not evidence for either one over the other . (These statements about the relative strength of evidence can be mathematically derived using Bayes' Theorem). </P>

A factor that is kept the same in scientific experiments