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 armpits with no rash. In many cases, itchy underarms are accompanied by a rash, but there are also many times when your armpits itch and there is no rash in sight. Common triggers of itchy armpits without a rash include excessive sweating, fever, weight loss, fatigue, dry skin, and swollen lymph nodes.