RESUMEN
Considerable attempts have been made to study the changes in lung function in man in different age groups using univariate statistical techniques in which the lung function tests were assumed to be independent of each other. Actually the lung function tests are well correlated with each other and, thus, the inferences drawn on the basis of univariate statistical analysis may be misleading due to the violation of the assumption of independence. On the other hand, simultaneous changes in lung function in man in different age groups cannot be tested using univariate statistical techniques. Keeping in view such shortcomings of the univariate statistical techniques, an attempt has been made in the present investigation to study simultaneous changes in some lung function tests [viz. vital capacity (VC), forced vital capacity (FVC), forced expiratory volume for one second (FEV1), expiratory reserve volume (ERV), inspiratory capacity (IC) and maximum voluntary ventilation (MVV)] at different age groups (viz. 21-25, 26-30, 31-35, 36-40, 41-45, 46-50, 51-55, 56-60 and 61-70 years) in healthy Indian males using multivariate statistical techniques (viz. Wilks' statistic (A) and Mahalanobis' D2 statistic) for drawing valid statistical inferences. It is concluded that remarkable significant changes take place in lung function after the age of forty years.