their uncertainties (such as confidence intervals) will be biased (not accurate on average). This is also true if the noise is heteroskedasticthat is, if it has different variances for different data points. Alternatively, in the subset of regression analysis known as time series analysis there are often no explanatory variables other than the past values of the variable being modeled (the dependent variable). In this case the noise process is often modeled as a moving average process, in which the current value of the dependent variable depends on current and past values of a sequential white noise process. Random vector transformations These two ideas are crucial in applications such as channel estimation and channel equalization in communications and audio. These concepts are also used in data compression. In particular, by a suitable linear transformation (a coloring transformation), a white random vector can be used to produce a "non-white" random vector (that is, a list of random variables) whose elements have a prescribed covariance matrix. Conversely, a random vector with known covariance matrix can be transformed into a white random vector by a suitable whitening transformation. Generation White noise may be generated digitally with a digital signal processor, microprocessor, or microcontroller. Generating white noise typically entails feeding an appropriate stream of random numbers to a digital-to-analog converter. The quality of the white noise will depend on the quality of the algorithm used. Informal use The term is sometimes used as a colloquialism to describe a backdrop of ambient sound, creating an indistinct or seamless commotion. Following are some examples: Chatter from multiple conversations within the acoustics of a confined space. The pleonastic jargon used by politicians to mask a point that they don't want noticed. Music that is disagreeable, harsh, dissonant or discordant with no melody. The term can also be used metaphorically, as in the novel White Noise (1985) by Don DeLillo which explores the symptoms of modern culture that came together so as to make it difficult for an individual to actualize their ideas and personality. See also References External links Noise (electronics) Statistical signal processing Data compression Sound Acoustics