69L NTERNATIONAL STANDARD TSO 3301 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION -MEX,IY HAPOIHAH OPrAHW3ALWI HO CTAHIAPTW3AWW.ORGANISATION INTERNATIONALE DE NORMALISATION Statistical interpretation of data - Comparison of two means in the case of paired observations Interpretation statistique des donnees -- Comparaison de deux moyennes dans le cas d'observations appariees First edition - 1975-08-15 ANs Internat Doc Sect No., Copies Date Recd at ANsI Cov Ltr. AUG-1-8.1975 Encl Sent to: 1 lalc ARrmTie Internatl filo 1 ISO 3301-1975 (E) UDC 519.28 Ref. No. ISO 3301-1975 (E) Des atisticalanalysis,mean,com nparison Price based on 6 pages Not for Resale FOREWORD ISO (the International Organization for Standardization) is a worldwide federation of national standards institutes (ISO Member Bodies). The work of developing International Standards is carried out through IsO Technical Committees. Every Member Body interested in a subject for which a Technical Committee has been set governmental and non-governmental, in iiaison with IsO, also take part in the work. Draft International Standards adopted by the Technical Committees are circulated to the Member Bodies for approval before their acceptance as International Standards by the ISO Council. International Standard ISO 3301 was drawn up by Technical Committee ISO/TC 69, Applications of statistical methods, and circulated to the Member Bodies in March 1974. It has been approved by the Member Bodies of the following countries : Austria India South Africa, Rep. of Beigium Israel Spain Brazil Switzerland Italy Turkey Czechoslovakia Netherlands France Poland United Kingdom Germany Portugal U.S.S.R. Hungary Yugoslavia Romania The Member Bodies of the following countries expressed disapproval of the document on technical grounds : Sweden U.S.A. @ International Organization for Standardization, 1975 Printed in Switzerland Not for Resale without it licensefrom IHS INTERNATIONAL STANDARD ISO 3301-1975 (E) Statistical interpretation of data -- Comparison of two means in the case of paired observations O INTRODUCTION hypothesis that there is no other systematic difference between the individuals in the same pair other than the The method specified in this International Standard, known systematic difference under test. as the method of paired observations, is a special case of the method described in table A' of ISO 2854, Statistical interpretation of data - Techniques of estimation and tests 3 FIELD OF APPLICATION relating to means and variances.1) The method may be applied to establish a difference between two treatments. In this case, the observations xi This special case is mentioned in section two of ISO 2854 are carried out after the first treatment and yi after the immediately after the numerical illustration of table A', and second treatment The two series of results of the a complete example of applications of the method of paired observations are not independent because each result x; of comparisons has been given in annex A of that the first series (first treatment) is associated with a result yi International Standard importance wide The and The term of the secondseries (second treatment). applicability of the method justify a separate International "treatment" should be understood in a wide sense. The two Standard being devoted to it treatments to be compared may, for instance, be two test methods, two measuring instruments or two laboratories, in order to detect a possible systematic error. Two treatments carried out successively on the same experimental material 1 SCOPE might interact and the value obtained might depend on the specifies a method for This International Standard order. Good experimental design should enable such biases comparing the mean of a population of differences between to be eliminated. Aiternatively, only one treatment may be paired observations with zero or any other preassigned applied and its effect may be compared to the absence of value. treatment; th