Financial decisions are influenced by psychological factors. Investors make typical mistakes which are well-documented in the literature. To test these mistakes we conduct a survey among German individual investors. Moreover we analyze whether socio demographic attributes experience, education and income affect behavior. The study shows that systematic mistakes are prevalent among German investors: they act according to the Self-Attribution Bias and the Endowment Effect. They overweight domestic stocks and anchor their decisions on irrelevant information. Representativeness and Herd Behavior is also prevalent. Among tested characteristics, education best predicts investor behavior. A higher level of education reduces Self-Attribution Bias, Anchoring and Representativeness significantly.