Even with similar results, scientists may wait until an investigation has been repeated many times before accepting the results as correct. Scientific knowledge is subject to modification as new information challenges prevailing theories and as a new theory leads to looking at old observations in a new way.
Some scientific knowledge is very old and yet is still applicable today.
Some matters cannot be examined usefully in a scientific way. Among them are matters that by their nature cannot be tested objectively and those that are essentially matters of morality. Science can sometimes be used to inform ethical decisions by identifying the likely consequences of particular actions, but cannot be used to establish that some action is either moral or immoral. Although there is no fixed set of steps that all scientists follow, scientific investigations usually involve the collection of relevant evidence, the use of logical reasoning, and the application of imagination in devising hypotheses and explanations to make sense of the collected evidence. If more than one variable changes at the same time in an experiment, the outcome of the experiment may not be clearly attributable to any one of the variables.