In other words, it describes the research that has not taken place before and their results.
In practice, the accumulation of evidence for or against any particular theory involves planned research designs for the collection of empirical data, and academic rigor plays a large part of judging the merits of research design.
In scientific use, the term empirical refers to the gathering of data using only evidence that is observable by the senses or in some cases using calibrated scientific instruments.
What early philosophers described as empiricist and empirical research have in common is the dependence on observable data to formulate and test theories and come to conclusions.
In some fields, quantitative research may begin with a research question (e.g., "Does listening to vocal music during the learning of a word list have an effect on later memory for these words? Usually, a researcher has a certain theory regarding the topic under investigation.
Based on this theory, statements or hypotheses will be proposed (e.g., "Listening to vocal voice has a negative effect on learning a word list.").
The researcher attempts to describe accurately the interaction between the instrument (or the human senses) and the entity being observed.
If instrumentation is involved, the researcher is expected to calibrate his/her instrument by applying it to known standard objects and documenting the results before applying it to unknown objects.
Research design varies by field and by the question being investigated.
Many researchers combine qualitative and quantitative forms of analysis to better answer questions which cannot be studied in laboratory settings, particularly in the social sciences and in education.