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In some specialist fields, the quasi-difference is the difference between two measured values or estimated values under the distorting influence of systematic errors ( trend ) or correlated measurement deviations. They can arise from the external circumstances of the measurement or from the calculation model . The former would be the case, for example, when determining a distance difference if the compared signals run through different layers of air or cannot be measured precisely simultaneously.
When taking measurements on the oscilloscope , a differential measurement of a quasi-difference z. B. differ by not completely suppressed common mode voltages of the two signals.

Similarly, quasi-differences in econometrics are a variant of dynamic DL models when special disturbance variables are effective. In the case of forecasts with quasi-differences, the question is whether a “soft” filter cannot be more suitable than a “hard” difference formation.

In the case of digital filters , the difference filter differs from the quasi-difference filter in that it has a transfer function that is usually applied exponentially.

In computing , the term quasi-difference is also used for calculating machines that work with numbers that are related to the values ​​represented by them in a non-linear transformation (e.g. quasi-sum or quasi-difference of logarithms ).

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