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The cephalic index or cranial index is a number obtained by taking the maximum width (biparietal diameter or BPD, side to side) of the head of an organism, multiplying it by 100 and then dividing it by their maximum length (occipitofrontal diameter or OFD, front to back). The index was once used to categorize human beings in the first half of ...
Cephalometric analysis depends on cephalometric radiography to study relationships between bony and soft tissue landmarks and can be used to diagnose facial growth abnormalities prior to treatment, in the middle of treatment to evaluate progress, or at the conclusion of treatment to ascertain that the goals of treatment have been met. [5]
If a data distribution is approximately normal then about 68 percent of the data values are within one standard deviation of the mean (mathematically, μ ± σ, where μ is the arithmetic mean), about 95 percent are within two standard deviations (μ ± 2σ), and about 99.7 percent lie within three standard deviations (μ ± 3σ).
In the Punjab study, the mesocephalic was the most common craniotype followed by dolicocephalic in the tropical regions. The brachycephalic was more common in the temperate regions. Genetic and environmental factors have been suggested for the presence of variations in cephalic indices among population groups.
The "68–95–99.7 rule" is often used to quickly get a rough probability estimate of something, given its standard deviation, if the population is assumed to be normal. It is also used as a simple test for outliers if the population is assumed normal, and as a normality test if the population is potentially not normal.
Bias in standard deviation for autocorrelated data. The figure shows the ratio of the estimated standard deviation to its known value (which can be calculated analytically for this digital filter), for several settings of α as a function of sample size n. Changing α alters the variance reduction ratio of the filter, which is known to be
Swedish professor of anatomy Anders Retzius (1796–1860) first used the cephalic index in physical anthropology to classify ancient human remains found in Europe. He classified brains into three main categories, "dolichocephalic" (from the Ancient Greek kephalê, head, and dolikhos, long and thin), "brachycephalic" (short and broad) and "mesocephalic" (intermediate length and width).
The anterior ratio is known to be 77.2%. An overall ratio of more than 91.3% means that the mandibular teeth are bigger when compared to normal. A ratio smaller than 91.3% would mean the mandibular teeth are smaller than normal. Anterior analysis follows the same principle. Having a different ratio than normal is referred to as Bolton Discrepancy.