These magma plumes rise to the surface and form chains of volcanoes. Composite volcano magma contains more silica, SiO 2, than that of a shield volcano and is therefore stickier (more viscous). This stickiness plugs up the volcano, causing pressure to build-up. The result is an explosive, dangerous eruption.
It results in a biased sample, a non-random sample of a population (or non-human factors) in which all individuals, or instances, were not equally likely to have been selected. If this is not accounted for, results can be erroneously attributed to the phenomenon under study rather than to the method of sampling.
Definition of Bias. Systematic error is also known as bias. It is any systematic process in the conduct of a study that results in the incorrect estimate of a measure of disease occurrence or measure of association.1  Because it is a systematic process, it will cause a distortion from the truth in a predictable (not random) direction.echnical Definition: It is the bias, in other words deviation from the truth, that it is caused when any measurement collected about or from subjects is not completely valid (i.e., not completely accurate).