The achieved sample size each month is approximately 1,000, and the response rate is around 40% of those asked to take part [ footnote 1 ].
Maint y sampl misol a gyrhaeddir yw tua 1,000, ac mae’r gyfradd ymateb tua 40% o’r rhai y gofynnwyd iddynt gymryd rhan [ troednodyn 1 ].