In these cases, a very small number of 'outliers' (observations that are markedly different from their base data values) can have a profound effect on the estimate. (
Yn yr achosion hyn, gall nifer fach iawn o “allanolynnau” (arsylwadau sy’n wahanol iawn i’w gwerthoedd data sylfaenol) gael effaith bellgyrhaeddol ar yr amcangyfrif. (