Standard deviation measures how far numbers in a data set are spread out from an average value. In investing, it is used as a measurement of portfolio volatility.

When you have the average production of three machines, it is easy to calculate the average or mean production. You just add up the three means and divide by three. But what if I want the average ...

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Right axis deviation occurs when the QRS axis is shifted between 90 and 180 degrees. A number of things can result in right axis deviation which include lung disease, right sided heart strain ...

Left axis deviation occurs when the QRS axis falls between -30 and -90. There are a variety of causes, including left anterior fascicular block and left ventricular hypertrophy. See the ECG basics ...