隨著產品不斷創新，消費者對產品屬性逐漸產生資訊不對稱之情形，故在選購產品時無法有明確的標的做為參考之依據，因而往往受到外部線索或外在刺激之影響進行購買行為。以往研究外部線索的相關議題中，皆只談到單一外部線索或兩種外部線索對產品評價進行討論，因此本研究將過去學者所提到之外部線索加以整合形成概念性架構，加以探討外部線索對消費者購買行為之影響。本研究共發放300份問卷，有效回收問卷224份，並利用線性結構關係模式（SEM）進一步驗證整體模式配適度，驗證結果顯示整體模式配適標準達檢定水準，表示本研究的理論模型可獲得支持，及代言人可信度、來源國形象、促銷活動、品牌形象等外部線索對產品評價皆有正向顯著的影響，而品牌形象與知覺風險在模式中亦具有中介效果之影響。

With product innovation, consumers are gradually unable to acquire full product attribute information, known as information asymmetry. Under information asymmetry, consumers' purchasing behaviors are usually under the influences of extrinsic cues or stimuli because consumers are lack of definite standards for reference. Previous studies related to issues of external cues, the discussion of product evaluation are only talking about one, or two external cues. In this research, there were 300 questionnaires distributed and 224 remained valid. Structural equation modeling (SEM) is also adopted to examine overall model fit. The research results show that the fittness standard of the global mode reach the statistical test level. It therefore means the theoretical model of this research is acceptable,and the two conclusions are as followed: All extrinsic cues comprising endorsers’ credibility, the image of country-of-origin, promotional activities, and brand image have positive significant effects on product evaluation. Results from structural equation modeling indicate that both brand image and perceived risk have mediating effects on the effects of endorsers' credibility, the image of country-of-origin, and promotional activities on product evaluation.