Probability distribution of random quantities, errors of a measurement (sources of errors, sorts of errors, recognition of errors), accuracy of a measurement, normal distribution, limit deviations and elimination of outlying measurements from a file of measuring results, systematic errors, law of random and systematic deviations propagation, weights of measured quantities, least squares method, adjustment of direct observations, pairs of measurements, adjustment of observation equations, adjustment of condition equations, line of regression, curve of regression.