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.
Common causes of itching. Itching can be caused by allergic reactions, skin conditions, insect bites, infections, or conditions that affect the body as a whole. Generalised pruritus without a rash (especially in people over the age of 65) is usually caused by dry skin. Sometimes it is not possible to determine the exact cause of the itch.