Quick Reference

1 The d.c. component of an a.c. signal.

2 The d.c. voltage used to switch on or off a bipolar transistor or diode (see forward bias, reverse bias), or the d.c. gate-source voltage used to control the d.c. drain-source current in a field-effect transistor. The word is also used as a verb: to switch.

3 The d.c. voltage or current used to set the operating point in linear amplifiers.

4 In statistical usage, a source of error that cannot be reduced by increasing sample size. It is systematic as opposed to random error.

Sources of bias include (a) bias in sampling, when members of the sample are not fully representative of the population being studied; (b) nonresponse bias in sample surveys, when an appreciable proportion of those questioned fail to reply; (c) question bias, a tendency for the wording of the question to invite an incorrect reply; (d) interviewer bias, a problem of personal interviewing when respondents try to reply in the way the interviewer is thought to expect.

A narrower definition of bias in statistical analysis (see statistical methods) is the difference between the mean of an estimating formula and the true value of the quantity being estimated. The estimatefor the variance of a population is biased, but is unbiased when n is replaced by (n–1).

5 (excess factor) See floating-point notation.

Subjects: Computing.

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