Improving the Quality of Shopping Center Sampling
描述了购物中心抽样的严谨程序，包括概率抽样和加权估计，以解决现有方法随意性大、难以推广的问题。
Shopping center sampling is popular because of low costs, but typical procedures are haphazard and thus generalization is difficult. In this article, procedures are described for careful sampling of shopping centers. They require probability sampling of the centers and of times and locations within centers. Finally, for unbiased estimates, data must be weighted by number of trips and imputations made for nonshoppers.