Missing answers are usually omitted from tables and analyses, except where they are of particular interest (e.g. a high level of “Don’t know” responses may be of substantive interest).
Gall atebion fod ar goll am sawl rheswm, gan gynnwys gwrthod neu fethu ateb cwestiwn penodol, ac achosion pan nad yw'r cwestiwn yn berthnasol i'r ymatebydd.