From sample surveys, officials estimate the population at the end of 2009 to have been 1.33 billion.

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For that, go to the sample surveys that India carries out more often.

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The figures are not strictly comparable, because sample surveys show the sex ratio at birth, whereas the census gives it among infants up to the age of six.

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On the basis of the national sample surveys (NSS), they calculate that India's sex ratio at birth swung from 924 females per 1, 000 males in 2004-05 to 977 in 2011, a stunning turnaround in favour of girls.

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And sample surveys of death certificates, followed by inquiries of the doctors concerned, indeed showed that by 2001 in 40% of all deaths the doctor either gave a painkiller that might shorten the patient's life, or simply ceased treatment.

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The National Federation of Independent Business (NFIB) conducts monthly surveys of a random sample of its 350, 000 members.

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Based on actual surveys and interviews with a random sample of debtors, the profs estimate that in 2003, at least 259, 000, or 15.7% of all bankruptcies, were really business-related.

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Jaime Gahche, main author of the CDC report, and her co-authors analyzed responses from a sample size of 37, 596, using National Health and Nutrition Examination surveys.

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Then they combined their findings with earlier surveys, which used other detection techniques, to create a statistical sample of stars and the planets that orbit them, which they say is representative of the galaxy.

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