Measurement uncertaintyIn metrology, measurement uncertainty is the expression of the statistical dispersion of the values attributed to a measured quantity. All measurements are subject to uncertainty and a measurement result is complete only when it is accompanied by a statement of the associated uncertainty, such as the standard deviation. By international agreement, this uncertainty has a probabilistic basis and reflects incomplete knowledge of the quantity value. It is a non-negative parameter.
Economic sectorOne classical breakdown of economic activity distinguishes three sectors: Primary: involves the retrieval and production of raw-material commodities, such as corn, coal, wood or iron. Miners, farmers and fishermen are all workers in the primary sector. Secondary: involves the transformation of raw or intermediate materials into goods, as in steel into cars, or textiles into clothing. Builders and dressmakers work in the secondary sector. Tertiary: involves the supplying of services to consumers and businesses, such as babysitting, cinemas or banking.
Propagation of uncertaintyIn statistics, propagation of uncertainty (or propagation of error) is the effect of variables' uncertainties (or errors, more specifically random errors) on the uncertainty of a function based on them. When the variables are the values of experimental measurements they have uncertainties due to measurement limitations (e.g., instrument precision) which propagate due to the combination of variables in the function. The uncertainty u can be expressed in a number of ways. It may be defined by the absolute error Δx.
Uncertainty quantificationUncertainty quantification (UQ) is the science of quantitative characterization and estimation of uncertainties in both computational and real world applications. It tries to determine how likely certain outcomes are if some aspects of the system are not exactly known. An example would be to predict the acceleration of a human body in a head-on crash with another car: even if the speed was exactly known, small differences in the manufacturing of individual cars, how tightly every bolt has been tightened, etc.
Secondary sector of the economyIn macroeconomics, the secondary sector of the economy is an economic sector in the three-sector theory that describes the role of manufacturing. It encompasses industries that produce a finished, usable product or are involved in construction. This sector generally takes the output of the primary sector (i.e. raw materials) and creates finished goods suitable for sale to domestic businesses or consumers and for export (via distribution through the tertiary sector).
Three-sector modelThe three-sector model in economics divides economies into three sectors of activity: extraction of raw materials (primary), manufacturing (secondary), and service industries which exist to facilitate the transport, distribution and sale of goods produced in the secondary sector (tertiary). The model was developed by Allan Fisher, Colin Clark, and Jean Fourastié in the first half of the 20th century, and is a representation of an industrial economy. It has been criticised as inappropriate as a representation of the economy in the 21st century.
Public sectorThe public sector, also called the state sector, is the part of the economy composed of both public services and public enterprises. Public sectors include the public goods and governmental services such as the military, law enforcement, infrastructure, public transit, public education, along with health care and those working for the government itself, such as elected officials. The public sector might provide services that a non-payer cannot be excluded from (such as street lighting), services which benefit all of society rather than just the individual who uses the service.
Primary sector of the economyThe primary sector of the economy includes any industry involved in the extraction and production of raw materials, such as farming, logging, fishing, forestry and mining. The primary sector tends to make up a larger portion of the economy in developing countries than it does in developed countries. For example, in 2018, agriculture, forestry, and fishing comprised more than 15% of GDP in sub-Saharan Africa but less than 1% of GDP in North America.
Tertiary sector of the economyThe tertiary sector of the economy, generally known as the service sector, is the third of the three economic sectors in the three-sector model (also known as the economic cycle). The others are the primary sector (raw materials) and the secondary sector (manufacturing). The tertiary sector consists of the provision of services instead of end products. Services (also known as "intangible goods") include attention, advice, access, experience and affective labour.
Voluntary sectorThe voluntary sector, independent sector, or civic sector is the realm of social activity undertaken by organizations that are non-governmental nonprofit organizations. This sector is also called the third sector, community sector, and nonprofit sector, in contrast to the public sector and the private sector. Civic sector or social sector are other terms for the sector, emphasizing its relationship to civil society. Richard Cornuelle coined the term "independent sector" and was one of the first scholars to point out the vast impact and unique mechanisms of this sector.
AfricaAfrica is the world's second-largest and second-most populous continent, after Asia in both aspects. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surface area. With billion people as of , it accounts for about of the world's human population. Africa's population is the youngest amongst all the continents; the median age in 2012 was 19.7, when the worldwide median age was 30.4.
South AfricaSouth Africa, officially the Republic of South Africa, is the southernmost country in Africa. It is bounded to the south by of coastline that stretches along the South Atlantic and Indian Oceans; to the north by the neighbouring countries of Namibia, Botswana, and Zimbabwe; and to the east and northeast by Mozambique and Eswatini. It also completely enclaves the country Lesotho. It is the southernmost country on the mainland of the Old World, and the second-most populous country located entirely south of the equator, after Tanzania.
