研究探讨网络购物中选择集大小对决策态度和行为的影响,以及目标确定性和产品类型对该关系的调节作用。采用2（大选择集vs.小选择集）×2（目标明确vs.目标不明确）×2（体验型产品vs.搜索型产品）的组间设计,发现大选择集组选择满意度、自信心更高,但延迟选择更多,出现态度-行为分离。目标不明确时,大选择集组延迟选择更多。

With the rapid development of e-commerce, online shopping behavior gets more and more attention. Consumers can just stay at home to enjoy shopping online. Shopping online not only saves a lot of time and energy costs, but also improves the possibility of consumers finding products to meet their needs. Sometimes consumers get benefit from plentiful options but sometimes they spend a lot of time and efforts and cannot find the satisfaction to meet their needs. Results of previous studies are inconsistent. A lot of studies have shown that the more choices there are, the better the online shopping experience; however, some researchers have found the ＂choice overload effect＂. The choice overload effect states that when the individual is faced with too many options compared to a smaller set of options, more negative results will ensue. For example, the lower degree of satisfaction, delaying selection, regret, the decline in self-confidence, or the reduction of buying behavior. A large number of studies in the past had been done, but the majority was on traditional shopping. The empirical research about the assortment size and the choice overload effect of online shopping is few. The present study aims to explore the effect of assortment size, target certainty and product type on consumer decision-making attitude and behavior for online shopping.  Three pretests and a main laboratory experiment have been conducted. First, we ran pretests 1 and 2 to select the specific product materials to be used in the main experiment, which would be used to indicate the main attributes for the experience product and the search product （beef jerky as experience product and USB flash drive as search product）. Second, we ran pretest 3 to make sure the option number for big and small selection was set （15 options as small selection set and 60 options as large one）. 125 students （41 for pretest 1, 54 for pretest 2 and 30 for pretest 3） participated in the pretests. It used a 2（large, small） × 2（certainty, uncertainty） × 2（experience product, search product） between-subject design in our main experiment. The participants＇ target certainty was manipulated by whether the participants needed to describe what they want. A total of 160 students （81 males and 79 females, M = 21.89, SD = 3.70） were randomly assigned to eight groups. They were first asked to read the instruction and imagine that they were doing online shopping. Then they were manipulated of target certainty and scanned the webpages we designed for each group. Finally, they completed a series of questions measuring their satisfaction, confidence and choice deferral.  The results showed the attitude-behavior separation, choice from large assortments were more likely to lead to higher satisfaction （M = 5.16 vs. 4.55）, higher confidence （M = 5.11 vs. 4.73） but more choice deferral （78.8% vs. 58.8%）. Target certainty moderated the effect of assortment size on choice deferral and target uncertainty individuals showed more choice deferral in the large assortments than in the small assortments （82.5% vs. 50.0%）, while target certainty individuals had similar choice deferral between different assortment size. Product type didn＇t moderate the effect of assortment size on choice deferral.  Comparing with prior studies on assortment size, our results suggested that in the online shopping environment, in terms of the attitude level, consumers still preferred large selection set, and the select-satisfaction and the self-confidence were higher than in the small selection set; however, in terms of the behavior level, in big choice set there were more negative buying behavior and consumers preferred to delay purchase. This study explored the choice overload effect and attitude-behavior separation on e-commerce, which had implications for webpage layout.