This dissertation contains research on different aspects of consumer purchasing behavior in electronic markets. In Herrmann, Kundisch and Rahman (2014), we analyze the effect of delegating decision making to IT on the occurrence of the sunk cost effect in subsequent decisions. Herrmann (2014) presents analytical results on the effect of the variance of online consumer ratings on equilibrium prices and demand. In Herrmann, Kundisch and Rahman (2013), we investigate the relationship between an aggressive bidding strategy and the likelihood of winning a pay-per-bid auction, and in Herrmann and Möller (2013), we empirically and experimentally investigate the impact of ad positioning on key performance indicators in search engine advertising. The dissertation is rounded off with Kundisch, Herrmann, Whittaker, Beutner, Fels, Magenheim, Reinhardt, Sievers und Zoyke. (2012). In this paper, we introduce and evaluate a web-based open source solution that enables the transfer of the widely established Peer Instruction approach to large lectures with in excess of 350 participants.