Observation is the active acquisition of information from a primary source.

Information is conveyed either as the content of a message or through direct or indirect observation.

The scientific method requires observations of natural phenomena to formulate and test hypotheses.

The purpose of an experiment is to determine whether observations agree with or conflict with the predictions derived from a hypothesis.

The scientific method requires observations of natural phenomena to formulate and test hypotheses.

For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous observations that cannot satisfactorily be explained with the available scientific theories.

Observations can be qualitative, that is, only the absence or presence of a property is noted, or quantitative if a numerical value is attached to the observed phenomenon by counting or measuring.

The process of measurement is central to quantitative research because it provides the fundamental connection between empirical observation and mathematical expression of quantitative relationships.

Field research involves a range of well-defined, although variable, methods: informal interviews, direct observation, participation in the life of the group, collective discussions, analyses of personal documents produced within the group, self-analysis, results from activities undertaken off- or on-line, and life-histories.

It is the practice and study of observing celestial objects with the use of telescopes and other astronomical instruments.

Introspection is closely related to human self-reflection and is contrasted with external observation.

Observations and Measurements (O&M) is an International Standard which defines a conceptual schema encoding for observations, and for features involved in sampling when making observations.

This is called the "streetlight effect".

The streetlight effect, or the drunkard's search principle, is a type of observational bias that occurs when people only search for something where it is easiest to look.

Systematic error may also refer to an error with a non-zero mean, the effect of which is not reduced when observations are averaged.

Observations can be qualitative, that is, only the absence or presence of a property is noted, or quantitative if a numerical value is attached to the observed phenomenon by counting or measuring.

In statistics, observable variable or observable quantity (also manifest variables), as opposed to latent variable, is a variable that can be observed and directly measured.

Clinical trials are experiments or observations done in clinical research.

Experimental physics is the category of disciplines and sub-disciplines in the field of physics that are concerned with the observation of physical phenomena and experiments.

Natural science is a branch of science concerned with the description, prediction, and understanding of natural phenomena, based on empirical evidence from observation and experimentation.

Observational cosmology is the study of the structure, the evolution and the origin of the universe through observation, using instruments such as telescopes and cosmic ray detectors.

Visible-light astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light (optical telescopes).

Qualitative research is a scientific method of observation to gather non-numerical data.

Experience is the knowledge or mastery of an event or subject gained through involvement in or exposure to it. Compare various contemporary definitions given in the OED (2nd edition, 1989): "[...] 3. The actual observation of facts or events, considered as a source of knowledge.[...] 4. a. The fact of being consciously the subject of a state or condition, or of being consciously affected by an event. [...] b. In religious use: A state of mind or feeling forming part of the inner religious life; the mental history (of a person) with regard to religious emotion. [...] 6. What has been experienced; the events that have taken place within the knowledge of an individual, a community, mankind at large, either during a particular period or generally. [...] 7. a. Knowledge resulting from actual observation or from what one has undergone. [...] 8. The state of having been occupied in any department of study or practice, in affairs generally, or in the intercourse of life; the extent to which, or the length of time during which, one has been so occupied; the aptitudes, skill, judgement, etc. thereby acquired."

Modern music psychology is primarily empirical; its knowledge tends to advance on the basis of interpretations of data collected by systematic observation of and interaction with human participants.

Each scientific law is a statement based on repeated experimental observations that describes some aspect of the Universe.

In addition to marksmanship and long range shooting, military snipers are trained in a variety of tactical techniques: detection, stalking, and target range estimation methods, camouflage, field craft, infiltration, special reconnaissance and observation, surveillance and target acquisition.

A traffic camera is a video camera which observes vehicular traffic on a road.

An observer is one who engages in observation or in watching an experiment.

The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion.