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.
Itchy skin, known as pruritus, makes you want to scratch until you get relief. What causes body itching? There are dozens of causes. -Dry skin: This usually results from hot or cold weather with low humidity, long-term use of air conditioning or central heating, and washing or bathing too much. -Skin conditions: Eczema, psoriasis, scabies, lice, chickenpox and hives all cause itchy skin.