Description of statistical samples in civil engineering. Measurement errors. Elements of probability theory. Discrete probability distribution. Continuous probability distributions: uniform on an interval, Normal distribution, t-distribution, Exponential distribution, x² distribution. Confidence interval and hypothesis testing concerning mean, variance and population. F-distribution. Correlation and covariance. Covariance propagation. Multi-dimensional Normal distribution. Error ellipse and error ellipsoid. Principles of least-squares estimation.