The arithmetic mean of a set of data. It provides a measure of the central tendency in the frequency distribution of the data. The other measures of central tendency are the median and the mode.
Average = Sum/Sample size
Sample: 5, 8, 12, 4, 7
Sample size = n = 5
Average = (5+8+12+4+6)/5 = 35/5 = 7
Mean, Median, and Mode.
NIST Statistics Handbook: Process Characterization - http://www.itl.nist.gov/div898/handbook/toolaids/pff/ppc.pdf