Standard Deviation (Volatility) Introduction. Standard deviation is a statistical term that measures the amount of variability or dispersion around an average. Standard deviation is also a measure of volatility. Generally speaking, dispersion is the difference between the actual value and the average value. The larger this dispersion or variability is, the higher the standard deviation. The smaller this dispersion or variability is, the lower the standard deviation.
MRI image showing a typical meningioma tumor. A meningioma is a tumor that arises from a layer of tissue (the meninges) that covers the brain and spine. Meningiomas grow on the surface of the brain (or spinal cord), and therefore push the brain away rather than growing from within it. Most are considered âbenignâ because they are slow-growing with low potential to spread. Meningioma tumors can become quite large. Diameters of 2 inches (5 cm.) are not uncommon.
Meningocele: A meningocele is a protrusion of the meninges that cover the brain or spinal cord through a bone defect in the skull or vertebral column respectively. The defect measures approximately 2 x 2 x 1.5 inches in size.