Fudge factor

Fudge factor

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A fudge factor is a quantity introduced into a calculation
A calculation is a deliberate process for transforming one or more inputs into one or more results, with variable change.The term is used in a variety of senses, from the very definite arithmetical calculation of using an algorithm to the vague heuristics of calculating a strategy in a competition...

 in order to "fudge" the results: that is, either to make them match better what happens in the real world, or to add an error margin . Fudge factors may be introduced retrospectively.

Examples in science

Some quantities in scientific theory are set arbitrarily according to measured results rather than by calculation (for example, Planck's constant). However, in the case of these fundamental constants, their arbitrariness is usually explicit. To suggest that other calculations may include a "fudge factor" may suggest that the calculation has been somehow tampered with to make results give a misleadingly good match to experimental data.

Cosmological constant

In theoretical physics, when Einstein originally tried to produce a general theory of relativity, he found that the theory seemed to predict the gravitational collapse of the universe: it seemed that the universe should either be expanding or collapsing, and to produce a model in which the universe was static and stable (which seemed to Einstein at the time to be the "proper" result), he introduced an expansionist variable (called the Cosmological Constant
Cosmological constant
In physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe...

), whose sole purpose was to cancel out the cumulative effects of gravitation. He later called this, "the biggest blunder of my life."

However it was later found that the constant was necessary. Current results record the constant to be non-zero to 99.7% certainty.

Fudge Float Factor

The FFF(fudge float factor) is a constant used when measuring the velocity of a river. The number is 0.85 and compensates for the action of the wind and tries to measure the internal flow.

Expected error margins

A common feature of "fudge factors" in science is their arbitrariness, and their retrospective nature.

However, in project management
Project management
Project management is the discipline of planning, organizing, securing, and managing resources to achieve specific goals. A project is a temporary endeavor with a defined beginning and end , undertaken to meet unique goals and objectives, typically to bring about beneficial change or added value...

 it's common to build a certain error margin into the predicted "resource cost" of a project to make predictions more realistic: there are many unforeseen factors that may delay a project or make it more costly, but very few factors that could result in it being delivered before time or under the calculated budget ... so to some degree, "unexpected" overruns are to be expected, even if their precise nature can't be predicted in advance. Experienced planners may know that a certain type of project will tend to overrun by a certain percentage of its calculated resource requirements, and may multiply the "ideal" calculations by a safety margin to produce a more realistic estimate, and this margin may sometimes be referred to as a fudge factor.
However, when planning ahead for expected unpredictabilities, these "error margins" are usually assigned other, more specific names : for instance in warehouse stock control, where a certain amount of stock is expected to disappear naturally through damage, pilfering or other unexplained problems, the discrepancy is referred to as shrinkage
Shrinkage (accounting)
In financial accounting the term inventory shrinkage is the loss of products between point of manufacture or purchase from supplier and point of sale. The term shrink relates to the difference in the amount of margin or profit a retailer can obtain...


In engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...

, a "fudge factor" may be introduced to allow a margin of error in unknown quantities .