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The simplest types of control are negative and positive controls, and both are found in many different types of experiments. [2] These two controls, when both are successful, are usually sufficient to eliminate most potential confounding variables: it means that the experiment produces a negative result when a negative result is expected, and a ...
Life-cycle assessment (LCA or life cycle analysis) is a technique used to assess potential environmental impacts of a product at different stages of its life. This technique takes a "cradle-to-grave" or a "cradle-to-cradle" approach and looks at environmental impacts that occur throughout the lifetime of a product from raw material extraction, manufacturing and processing, distribution, use ...
Life cycle energy analysis (LCEA) is an approach in which all energy inputs to a product are accounted for, not only direct energy inputs during manufacture, but also all energy inputs needed to produce components, materials and services needed for the manufacturing process. [110] With LCEA, the total life cycle energy input is established. [111]
The C2C concept ignores the use phase of a product. According to variants of life-cycle assessment (see: Life-cycle assessment § Variants) the entire life cycle of a product or service has to be evaluated, not only the material itself. For many goods e.g. in transport, the use phase has the most influence on the environmental footprint.
The technology life cycle (TLC) describes the commercial gain of a product through the expense of research and development phase, and the financial return during its "vital life". Some technologies, such as steel, paper or cement manufacturing, have a long lifespan (with minor variations in technology incorporated with time) while in other ...
[1] [2] [3] This issue arises when a bad control is an outcome variable (or similar to) in a causal model and thus adjusting for it would eliminate part of the desired causal path. In other words, bad controls might as well be dependent variables in the model under consideration. [ 3 ]
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Consider a study about whether getting older affects someone's life satisfaction. (Some researchers perceive a "u-shape": life satisfaction appears to decline first and then rise after middle age. [5]) To identify the control variables needed here, one could ask what other variables determine not only someone's life satisfaction but also their age.