  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.
