The first observations could be data obtained from the library or information from your own experience.

Another source of observations could be from trial experiments or past experiments.  These observations, and all that follow, must be empirical in nature – that is, they must be sensible, measurable, and repeatable, so that others can make the same observations.

The systematic, collection of measurements or counts of relevant quantities is the basis of empirical technique. Scientific measurements taken are often tabulated, graphed, or mapped, and statistical manipulations, such as correlation and regression, performed on them. Measurements often require specialized scientific instruments and the progress of a scientific field is usually intimately tied to their invention and development.

Empirical evidence is evidence that one can see, hear, touch taste, or smell; it is evidence that is susceptible to one’s senses. Empirical evidence is important because it is evidence that others besides yourself can experience, and it is repeatable, so empirical evidence can be checked by yourself and others after knowledge claims are made by an individual.

Empirical evidence is the only type of evidence that possesses these attributes and is therefore the only type used by scientists and critical thinkers to make vital decisions and reach sound conclusions. Another way to phrase empirical evidence might be: the evidence found in nature.

• Measurements in scientific work are also usually accompanied by estimates of their uncertainty.
• The uncertainty is often estimated by making repeated measurements of the desired quantity.
• Counts of things may also have an uncertainty due to limitations of the method used.
• A scientific quantity is described or defined by how it is measured, this is known as the operational definition.

For example, electrical current, measured in amperes, may be operationally defined in terms of the mass of silver deposited in a certain time on an electrode in an electrochemical device that is described in detail. The operational definition of a thing often relies on comparisons with standards: the operational definition of “mass” ultimately relies on the use of an artifact i.e. carbon 12 as it is used as the standard from which atomic masses of all nuclides are measured – its atomic mass is by definition 12.

Scientific method depends upon sophisticated characterizations of subjects of the investigation. The subjects can also be considered lists of unsolved problems or the unknowns. The scientific process involves the gathering of relevant information in an attempt to answer the question or solve the problem by making observations.

The element of observation includes both unconditioned observations (prior to any theory) as well as the observation of the experiment and its results. The elements of experiment design must consider the elements of hypothesis development, prediction, plus the effects and limits of observation because all of these elements are typically necessary for a valid experiment.