scores (ie. .55, -.57 and -.44). Reasonably high communality values in the final statistics suggested the variables were well defined by the three factor solution (Table 3) and the percentage of total variance explained by this solution amounted to 80.6%, with the first principal component accounting for 47.1%. The Schoneil Reading Test had the highest factor loading on the first principal component, with 93% of the variance in its scores explained by the common factors in the solution. At this high degree of representation, such a variable would provide a rough and
dirty method for the measurement of acculturation.
Factor Interpretation
With a cut off factor loading of 0.3 for inclusion of a variable in the interpretation of the 3 principal components, all variables in the final solution were retained and most were complex after varimax rotation (Table 4). All the variables loading on the first principal component were complex and related to reading ability. The verbal abilities required for this western skill can be described by Thurstone's group factor, "v erbal c o m p r e h e n s i o n " (Thurstone 1938, 1941 cited in Anastasi 1976 p372). Anastasi (1976) considered vocabulary tests to be an adequate measure for this group factor. Some variance in the easier reading test scores were attributed to the second principal component after rotation, while the more difficult vocabulary tests (ie. NART and WAISR Vocabulary) loaded partially on the third principal component. The second principal com ponent was distinctively represented by the variable Age. As this variable had a negative loading, younger patients tended to read better and grew up nearer european settlements more often than older patients. Thus, the second principal component was interpreted as y o u t h f u l n e s s. The third principal component was uniquely represented by the variable m easuring frequency of English Language Use. Complex variables consisting of more difficult english language vocabulary (ie. NART and WAISR Vocabulary) and degree of Urbanisation also loaded on this component. Patients who used the english language more often and who
grew up n e arer eu ro p ean se ttlem en ts, were b e tter skilled in d iffic u lt e n g lis h v o c a b u la r y than o th ers. T h u s , the third c o m p o n e n t was considered to represent standard english language abi lit y.
Neurome di cal Risk Scale
F act or A nal ys is
P rin c ip le co m p o n e n ts extraction w ith v arim ax o rth o g o n al ro tatio n was p erform ed w ith SPSS Factor procedure for the M acintosh, on 7 variables m easu rin g deg ree of N eurom edical R isk for brain im pairm ent. As with A c c u ltu r a tio n , m ean scores w ere s u b s titu te d fo r m issing v a lu e s, no a tte m p t w as m ade to ex clu d e p a tie n t o u tlie rs and only o rth o g o n a l ro tatio n was co n sid ered appropriate to derive facto r scores to form a com posite m easure of N eurom edical Risk for later m ultivariate regression a n a ly s is .
Model Diagn ostics
D ia g n o s tic s o u tlin e d in N o ru s is (1 9 9 0 ) w ere u sed to d e v e lo p an appropriate factor model for the NM R data. The final analysis produced a 3 factor solution for the complete set of 7 NMR variables. Although 38% of the variables correlated with each other by at least 0.30, only 28.6% were significant (ie. 1 tailed, p<0.05). Bartlett's test of sphericity failed to reject the hypothesis that the c o rrelatio n m atrix was an identity m atrix (ie. B T S= 26.63, p=.184), but its level of significance was not considered large enough to completely rule out use of the factor model to explain the data. T he K aiser-M ey er-O lk in m easure of overall sam pling adequacy of the variables was acceptable but m iserable (ie. 0.579); 61.9% of the off- diagonal coefficients of the AIC were >0.09; and 66.0% of the residuals of the re p ro d u c e d correlation matrix were greater than 0.05 in m agnitude. AGE failed to correlate significantly with any other NMR variable. When it was r e m o v e d from the s o lu tio n , the m o d el d ia g n o s tic s m a rg in a lly im p ro v e d . F o r exam ple, B artlett's test rea ch e d sig n ifican ce (p=0.040);