SiO 2. One of the most common minerals in the world, quartz can be found in sedimentary, metamorphic, and igneous rocks throughout Virginia. Quartz typically appears as clear or whitish crystals within a rock such as granite.Amethyst, agate, chalcedony, chert (flint), and opal are all varieties of quartz.iO 2. One of the most common minerals in the world, quartz can be found in sedimentary, metamorphic, and igneous rocks throughout Virginia. Quartz typically appears as clear or whitish crystals within a rock such as granite.
First, calculate the deviations of each data point from the mean, and square the result of each: The variance is the mean of these values: and the population standard deviation is equal to the square root of the variance: This formula is valid only if the eight values with which we began form the complete population.
The variance (Ï 2), is defined as the sum of the squared distances of each term in the distribution from the mean (Î¼), divided by the number of terms in the distribution (N). There's a more efficient way to calculate the standard deviation for a group of numbers, shown in the following equation: You take the sum of the squares of the terms in the distribution, and divide by the number of terms in the distribution (N). From this, you subtract the square of the mean (Î¼2). It's a lot less work to calculate the standard deviation this way.