Is prior knowledge of a programming language important for software quality?

Software engineering is human intensive. Thus, it is important to understand and evaluate the value of different types of experiences, and their relation to the quality of the developed software. Many job advertisements focus on requiring knowledge of specific programming languages. This may seem sensible at first sight, but maybe it is sufficient to have general knowledge in programming and then it is enough to learn a specific language within the new job. A key question is whether prior knowledge actually does improve software quality. This paper presents an empirical study where the programming experience of students is assessed using a survey at the beginning of a course on the Personal Software Process (PSP), and the outcome of the course is evaluated, for example, using the number of defects and development time. Statistical tests are used to analyse the relationship between programming experience and the performance of the students in terms of software quality. The results are mostly unexpected, for example, we are unable to show any significant relation between experience in the programming language used and the number of defects detected.