[ Date Index ] [ Thread Index ] [ <= Previous by date / thread ] [ Next by date / thread => ]
james kilty wrote:
Not quite - that is the annual survey. I'm talking about a census. And they will be ignoring about 40% if they choose to ignore small farms and below - that's not even a survey - that's the back of a fag packet! https://statistics.defra.gov.uk/esg/ace/b1_data.htm and that's without very small (300,000 of them I think I found elsewhere)On Wed, 2010-02-03 at 15:06 +0000, richard wrote: snipfor their justification of their method see ; http://www.defra.gov.uk/esg/work_htm/publications/cs/farmstats_web/1_ABOUT_THE_SURVEY/FAQs_ABOUT_THE_DATA_AND_SURVEY/Introduction.htm#samplingstrategyThe sampling seems OK to me. Even though they "sample" all the biggies, they sample from all their strata and multiply up to estimate the contribution of all strata. The key para is Within each stratum holdings are sampled at random. The only exception to this is amongst the smallest holdings where a partially systematic approach is adopted to ensure that individual holdings are not usually sampled in successive years. This departure from randomness does create some risk of bias, but this risk is small, particularly since this stratum makes a relatively small contribution to the national totals for most crops. James
Tom te tom te tom -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html