Background: The relation between software effort and size has been modeled in literature as exponential, in the sense that the natural logarithm of effort is expressed as a linear function of the logarithm of size. The common approach to estimate the parameters of the linear model is ordinary least squares regression which has been extensively applied to various datasets. The least squares estimation takes into account only the error arising from the dependent variable (effort), while the measurement of independent variable (size) is considered free of errors. Aims: The basis of the study is that in practice the assumption of measuring the size without error is hardly true, since the size of a software project depends on the precision of the tool of measurement and often by the subjectivity of the rater. Moreover, the sizes of projects comprising a dataset have been measured by different measurement tools and this adds another source of variability in the independent variable. Method:...