This book provides an introduction to econometrics through a thorough grounding in probability theory and statistical inference. The emphasis is on the concepts and ideas underlying probability theory and statistical inference, and on motivating the learning of them both at a formal and an intuitive level. By basing its approach on the underlying theory, it is able to cover fully the econometric theory required up to the intermediate level; its emphasis on mastering the concepts makes it an ideal introduction to the advanced texts and the econometric literature.