Procedure to Approximately Estimate the Uncertainty of Material Ratio   Parameters due to Inhomogeneity of Surface Roughness
  Roughness parameters that characterize contacting surfaces with regard to friction and wear are commonly stated without uncertainties, or with an uncertainty only taking into account a very limited amount of aspects such as repeatability of reproducibility (homogeneity) of the specimen. This makes it difficult to discriminate between different values of single roughness parameters.   Therefore uncertainty assessment methods are required that take all relevant aspects into account. In the literature this is scarcely performed and examples specific for parameters used in friction and wear are not yet given.   We propose a procedure to derive the uncertainty from a single profile employing a statistical method that is based on the statistical moments of the amplitude distribution and the autocorrelation length of the profile. To show the possibilities and the limitations of this method we compare the uncertainty derived from a single profile with that derived from a high statistics experiment. 
Dorothee H\"user, Jonathan H\"user, Sebastian Rief, J\"org Seewig,   Peter Thomsen-Schmidt
physics.data-an