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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 were corrected and subsequent processes have yielded data of excellent quality. The design and implementation of the survey detailed the protocol for training the field staff for data collection and office staff for data entry and how to properly check and clean the data. These procedures have become an established part of work in China after regional staff completec extended trips to the U.S. for training. In fact, the China Institute felt these visits were so important, that they allocated additional scarce foreign exchange funds from their own budget for this training to take place.

The internal controls on quality measures have been 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 have allowed the development household-specific measurements for factors that truly vary by such an amount as to change energy intake for family members by 12 to 15 percent, depending on the use of average or household-specific measures. For income, family composition, and other measures, similar checks have been used to provide much more precise refinement of important factors.