what is the arithmetic mean 
the arithmetic mean is the simplest and most widely used measure of a mean or average it simply involves taking the sum of a group of numbers then dividing that sum by the count of the numbers used in the series for example take the numbers 34 44 56 and 78 the sum is 212 the arithmetic mean is 212 divided by four or 53 people also use several other types of means such as the geometric mean and harmonic mean which comes into play in certain situations in finance and investing another example is the trimmed mean used when calculating economic data such as the consumer price index cpi and personal consumption expenditures pce investopedia jiaqi zhou