measure of central tendency quartile center value The median is that value of the variate which divides the total frequency into two halves. The median is measure of central tendency of data. It is obtained by arranging the observations in order from smallest to largest value. If there is an odd number of observations, the median is the middle value. If there is an even number of observations, the median is the average of the two middle values. replaced OBI import following addition of restrictions and use in STATO. however the xref to OBI is kept as class metadata PRS and AGB added restriction about 'measure of central tendency' and quartile, june 2013 on 'centre value' OBI class. median center value (http://purl.obolibrary.org/obo/OBI_0000674) second quartile A Dictionary of Statistical Terms, 5th edition, prepared for the International Statistical Institute by F.H.C. Marriott. Published for the International Statistical Institute by Longman Scientific and Technical. and Wolfram Alpha http://purl.obolibrary.org/obo/OBI_0000674 Alejandra Gonzalez-Beltran Philippe Rocca-Serra ready for release