Agile methods are currently the dominant way of software development. This thesis presents the main principles of agile software development with emphasis on the method Scrum and some of the group techniques for software estimation. Planning poker is the most often used technique for estimating the size of user stories, but lately Team estimation game has been gaining popularity too, so emphasis was put on these two. An accuracy analysis of user story estimates based on data, collected during a study that was carried out at Software Engineering course in year 2014/15, was performed. Design of the study and the process of collecting the data is described. The data was analysed using appropriate statistical methods and the results were explained in detail. The goal of the thesis was to find out how final estimates obtained through Planning poker differ from the statistical combination of the estimates obtained during the first round of the process and whether there is a statistically important difference between the estimates obtained through Planning poker and those obtained through TEG. Our analysis showed that Planning poker decreased the over-optimism present in the statistical combination of initial estimates. However, the size of effect was very small. Estimates obtained through TEG were even less optimistic than those obtained through Planning poker. Accuracy analysis of estimates showed no statistically significant difference.