TESTS OF DATA QUALITY, SCALING ASSUMPTIONS, AND RELIABILITY OF THE SF-36 IN 11 COUNTRIES - RESULTS FROM THE IQOLA PROJECT

Data from general population samples in II countries (n = 1483 to 9151 ) were used to assess data quality and test the assumptions underlying the construction and scoring of multi-item scales from the SF-36 Heal th Survey. Across all countries, the rate of item-level missing data g enerally was low, although slightly higher for items printed in the gr id format. In each country, item means generally were clustered as hyp othesized within scales: Correlations between items and hypothesized s cales were greater than 0.40 with one exception, supporting item inter nal consistency. Items generally correlated significantly higher with their own scale than with competing scales, supporting item discrimina nt validity. Scales could be constructed for 93-100% of respondents. I nternal consistency reliability of the eight SF-36 scales was above 0. 70 for all scales, with two exceptions. Floor effects were low for all except the two role functioning scales; ceiling effects were high for both role functioning scales and also were noteworthy for the Physica l Functioning, Bodily Pain, and Social Functioning scales in some coun tries. These results support the construction and scoring of the SF-36 translations in these II countries using the method of summated ratin gs. (C) 1998 by Elsevier Science Inc.