measure of central tendency average value http://purl.obolibrary.org/obo/OBI_0000679 The arithmetic mean is defined as the sum of the numerical values of each and every observation divided by the total number of observations. S The arithmetic mean A is defined by the formula A=sum[Ai] / n where i ranges from 1 to n and Ai represents the value of individual observations. The arithmetic mean is significantly affected by extreme values and outliers. A better measure of central tendency is the median (http://purl.obolibrary.org/obo/STATO_0000574). average value (http://purl.obolibrary.org/obo/OBI_0000679) Alejandra Gonzalez-Beltran STATO replaced OBI import following addition of restrictions and use in STATO. however the xref to OBI is kept as class metadata arithmetic mean http://docs.scipy.org/doc/numpy/reference/generated/numpy.mean.html Philippe Rocca-Serra ready for release