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.
Contact with insects or parasites is another common cause of itching. Mosquito bites, flea bites, and lice infestations can often result in itchy skin. While annoying, these conditions are easily treated with over-the-counter remedies. Various kinds of infection can also cause itching without rash. Vaginal itching in women is often caused by a fungal or yeast infection. Athleteâs foot is another example of an itchy fungal infection that doesn't usually cause a rash.