The empirical method is generally taken to mean the approach of using a collection of data to base a theory

Theory

The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...

 or derive a conclusion in science

Science

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...

. It is part of the scientific method

Scientific method

Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

, but is often mistakenly assumed to be synonymous with the experimental method

Experiment

An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

.
The empirical method is not sharply defined and is often contrasted with the precision of the experimental method, where data are derived from the systematic manipulation of variables in an experiment. Some of the difficulty in discussing the empirical method is from the ambiguity of the meaning of its linguist root: empiric.

According to Oxford English Dictionary

According to the Oxford English Dictionary

Oxford English Dictionary

The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

 (2nd Edition, 1989), empiric is derived from the ancient Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 for experience, , which is ultimately derived from in + trial, experiment. Therefore, empirical data is information that is derived from the trials and errors of experience. In this way, the empirical method is similar to the experimental method. However, an essential difference is that in an experiment the different "trials" are strictly manipulated so that an inference can be made as to causation of the observed change that results. This contrasts with the empirical method of aggregating naturally occurring data.

Adding further confusion is another connotation of empiric. Strict empiricists are those who derive their rules of practice entirely from experience, to the exclusion of philosophical theory.

The OED further states that an empiric is "one who, either in medicine or in other branches of science, relies solely upon observation and experiment" [emphasis added]. In this case, an empiricist can be someone who conducts an experiment but without using a hypothesis to guide the process, i.e., strictly by the trial-and-error method. This is counter to one of the main tenets of the scientific method, that of the hypothetico-deductive method, where the manipulation of the variable in an experiment is dictated by the hypothesis being tested.

According to McGraw-Hill

The empirical method is generally characterized by the collection of a large amount of data before much speculation as to their significance, or without much idea of what to expect, and is to be contrasted with more theoretical methods in which the collection of empirical data is guided largely by preliminary theoretical exploration of what to expect. The empirical method is necessary in entering hitherto completely unexplored fields, and becomes less purely empirical as the acquired mastery of the field increases. Successful use of an exclusively empirical method demands a higher degree of intuitive ability in the practitioner.