Unobserved

Unobserved is an adjective meaning not observed; not seen or noticed; not recorded or reported. It is often used to describe phenomena, data, or variables that are present but remain outside the scope of direct observation or measurement.

In statistics and research design, unobserved variables are those that influence outcomes but are not directly measured. They are also called latent variables. Unobserved confounding refers to the influence of variables that affect both the treatment and outcome but are not observed, which can bias estimates. Analysts address this with latent-variable models, instrumental variables, or sensitivity analysis. Missing data can be described as unobserved values that should have been observed but were not recorded.

In science, unobserved phenomena include events or objects that lie beyond current detection capabilities. In physics and cosmology, concepts such as dark matter or certain quantum states may be unobserved but inferred from indirect evidence. In experimental settings, an unobserved state or outcome denotes something that exists but is not detected within a measurement process, such as a particle’s hidden state in a hidden Markov model.

In everyday language, unobserved simply means not seen or noticed by observers, which can refer to people, intentions, or occurrences.

See also latent variable, hidden variable, missing data, unobserved confounding.