Introduction. The standard deviation is a measure of the spread of scores within a set of data. Usually, we are interested in the standard deviation of a population. However, as we are often presented with data from a sample only, we can estimate the population standard deviation from a sample standard deviation.ntroduction. The standard deviation is a measure of the spread of scores within a set of data. Usually, we are interested in the standard deviation of a population. However, as we are often presented with data from a sample only, we can estimate the population standard deviation from a sample standard deviation.
Itching usually results from dry skin, a skin disorder, or an allergic reaction. If the person has no rash or skin abnormalities, the cause may be a drug, an allergic reaction that has internal effects, or a systemic disorder.
Itching all over (pruritis) is an annoying sensation often caused by skin irritation or inflammation. Itching all over may be associated with a rash or other skin symptoms, or it may occur by itself. Itching all over can be caused by a relatively mild condition, such as dry skin and a build-up of dead skin cells. For example, if you feel itchy all over and you live in a dry climate, you may have âwinter itchâ caused by the lack of moisture in your skin.