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.
Pruritus can be caused by many conditions. One common cause of itch is psychological, that is, due to stress, anxiety, or other emotional problems. Stress also can aggravate itch from other causes. Dry skin (xerosis) is perhaps the most frequent cause of itch without a rash.ruritus can be caused by many conditions. One common cause of itch is psychological, that is, due to stress, anxiety, or other emotional problems. Stress also can aggravate itch from other causes. Dry skin (xerosis) is perhaps the most frequent cause of itch without a rash.