This paper provides a review of the models of ambiguity and ambiguity aversion within the framework of subjective utility theory, and in chapters 2 and 3 develops applications of these models. In chapter 2, a model of status quo bias is presented and related literature is discussed. I show that an ambiguity averse decision-maker has an incentive to keep the `"mediocre" status quo unchanged. In chapter 3, a model of voting under ambiguity of candidate platforms is proposed. I show that under certain circumstances, the voters have an incentive to abstain from voting and the candidates are inclined to take more extreme positions.