  We present a new analysis of previously published optical and radio data sets
of the gravitationally lensed quasar 0957+561 A,B with the aim of determining
the time delay between its two images. We use a non-parametric estimate of the
dispersion of the combined data set where, however, we only make use of
alternating neighbours in order to avoid windowing effects.
  From the optical data a time delay of (415 $\pm$ 32) days and from the radio
data a delay of (409 $\pm$ 23) days is suggested. We demonstrate a considerable
sensitivity of different delay estimation procedures against the removal of
only a few observational data points or against smoothing or detrending of the
original data sets. The radio data give us formally a slightly more precise
value for the time delay than the optical data. Also, due to the lack of
windowing effects, the result obtained for the radio data can be considered as
somewhat more reliable than the delay determined from the optical data.
