typei

Type I is a designation used in various scientific disciplines to label a first or primary class within a category, with the exact meaning depending on the context.

In statistics, a Type I error is the incorrect rejection of a true null hypothesis, a false positive. It is controlled by the significance level alpha. Reducing the probability of Type I errors often increases the risk of Type II errors, which are false negatives.

In astronomy, a Type I supernova refers to a thermonuclear explosion of a white dwarf in a binary system, producing what are commonly called Type Ia supernovae. Type Ia supernovae are used as standard candles for measuring cosmic distances and typically exhibit spectral features such as silicon lines, with a lack of hydrogen in their spectra.

In condensed matter physics, Type I superconductors expel magnetic fields completely below a critical temperature and a single critical field, through the Meissner effect. They contrast with Type II superconductors, which allow partial magnetic flux penetration and exhibit a mixed state between lower and upper critical fields.

In string theory, Type I string theory is a version that includes open and unoriented strings, typically with the gauge group SO(32) in ten dimensions. It is distinct from Type II and heterotic string theories and involves objects such as D-branes and orientifold planes.

The term may appear in other domains as well. Clarifying the relevant field is essential to determine the precise meaning of "type I."