Unité statistique

In statistics, a unit is one member of a set of entities being studied. It is the main source for the mathematical abstraction of a "random variable". Common examples of a unit would be a single person, animal, plant, manufactured item, or country that belongs to a larger collection of such entities being studied. Units are often referred to as being either experimental units, sampling units or units of observation: An "experimental unit" is typically thought of as one member of a set of objects that are initially equal, with each object then subjected to one of several experimental treatments. Put simply, it is the smallest entity to which a treatment is applied. A "sampling unit" is typically thought of as an object that has been sampled from a statistical population. This term is commonly used in opinion polling and survey sampling. For example, in an experiment on educational methods, methods may be applied to classrooms of students. This would make the classroom as the experimental unit. Measurements of progress may be obtained from individual students, as observational units. But the treatment (teaching method) being applied to the class would not be applied independently to the individual students. Hence the student could not be regarded as the experimental unit. The class, or the teacher by method combination if the teacher had multiple classes, would be the appropriate experimental unit. In most statistical studies, the goal is to generalize from the observed units to a larger set consisting of all comparable units that exist but are not directly observed. For example, if we randomly sample 100 people and ask them which candidate they intend to vote for in an election, our main interest is in the voting behavior of all eligible voters, not exclusively on the 100 observed units. In some cases, the observed units may not form a sample from any meaningful population, but rather constitute a convenience sample, or may represent the entire population of interest.

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Concepts associés (2)

Séances de cours associées (6)

Blocking (statistics)

In the statistical theory of the design of experiments, blocking is the arranging of experimental units that are similar to one another in groups (blocks). Blocking can be used to tackle the problem of pseudoreplication. Blocking reduces unexplained variability. Its principle lies in the fact that variability which cannot be overcome (e.g. needing two batches of raw material to produce 1 container of a chemical) is confounded or aliased with a(n) (higher/highest order) interaction to eliminate its influence on the end product.

Statistique

La statistique est la discipline qui étudie des phénomènes à travers la collecte de données, leur traitement, leur analyse, l'interprétation des résultats et leur présentation afin de rendre ces données compréhensibles par tous. C'est à la fois une branche des mathématiques appliquées, une méthode et un ensemble de techniques. ce qui permet de différencier ses applications mathématiques avec une statistique (avec une minuscule). Le pluriel est également souvent utilisé pour la désigner : « les statistiques ».

Blocking probability of large wood and resulting head increase at ogee crest spillways

Paloma Furlan

Large wood increases the hydraulic complexity of rivers, yet it may block and modify the flood discharge capacity of hydraulic structures such as bridges and spillways. When spillway blockage occurs, dangerous and hazardous situations have been observed at ...

EPFL2019

Experimental repetitions and blockage of large stems at ogee crested spillways with piers

Anton Schleiss, Michael Pfister, José Pedro Gamito de Saldanha Calado Matos, Paloma Furlan

Large wood is often transported by rivers into reservoirs during heavy rainfall events. When a critical section like a spillway is blocked and discharge capacity reduced, an uncontrolled increase of the reservoir water level may occur. This study aims to s ...

2018

Explore la turbulence, la symétrie et l'impact du nombre de Reynolds sur le comportement du flux.

Explore les concepts de physique statistique dans des systèmes isolés, en se concentrant sur l'entropie et le désordre.

Explore les modèles de dispersion et le coefficient de dispersion axiale dans les systèmes fluides.