Quality Control Procedures

Extensive changes were made to substantially increase quality control for the 1991 and 1993 rounds of the CHNS after some problems were uncovered in the procedures of several provinces as part of the CHNS 1989 activities. Those problems have been corrected and the CHNS 1989 data are now of high quality. The design and implementation of the training of field staff involved in data collection and office staff handling data entry, checking, and cleaning have become an established part of work in China. Extended trips to the U.S. for training and data processing staff have helped with this effort. The Institute felt these visits were so important that they allocated additional scarce foreign exchange funds from their own budget for this training.

The internal controls on quality of measurement are based on collecting measures of selected factors from multiple perspectives and then using these data to refine measurement. One example is dietary fat. Typically, an average amount of fat used on a dish-by-dish basis is used to estimate fat intake. This procedure is also used for other condiments and minor food elements. In this study, the household measures allow us to develop household-specific measurements for factors which truly vary by such an amount as to change energy intake for family members by 12-15 percent, depending on the use of average or household-specific measures. For income, family composition, and other measures, similar checks are used to provide much more precise refinement of important factors.