modulation

n. changes in some parameter of a waveform (e.g., amplitude, frequency, phase) so that the information contained by the variations of this parameter can be transmitted by the wave, which is known as the carrier wave. Amplitude modulation (AM) refers to changes in amplitude that are relatively slow compared to the usually sinusoidal variations in the carrier. In frequency modulation (FM), the frequency of the carrier is varied, but its amplitude remains constant. In phase modulation, the relative phase of the carrier wave is varied in accordance with the amplitude of the signal variations. For most modulated waveforms, the frequency of modulation is much less than the frequency components in the carrier.

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Psychology term of the day

May 9th 2024

hierarchically nested design

any research design that involves several levels of sampling, such that the entities on the lower levels of the design are nested or subsumed within higher order groups. For example, a hierarchically nested design for an educational study might involve students (A), who are nested within classrooms (B), which are nested within schools (C), which are further nested within school districts (D). Several statistical procedures (e.g., analysis of variance, regression analysis, hierarchical linear models) also incorporate a hierarchical aspect. Also called hierarchical design; nested design.