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.
A common cause of itching is psychological brought on by stress or other emotional problems. The skin is the largest organ on your body and anxiety attacks this organ with an irritating itch. Not only that, but stress can aggravate other skin problems such as eczema and psoriasis. Stress also causes the body to produce hormones such as cortisol which cause the sebaceous glands to produce more oil making the skin more prone to problems.