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Sample Design

STATISTICAL INSTITUTE OF JAMAICA. Sample Design. Establishments Surveys. Stuart Brown Research, Design & Evaluation January 2013. Sampling Frame. The Business Register (or Central Register of Economic Units - CREU) Does not include agricultural/government establishments

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Sample Design

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  1. STATISTICAL INSTITUTE OF JAMAICA Sample Design Establishments Surveys Stuart Brown Research, Design & Evaluation January 2013

  2. Sampling Frame • The Business Register (or Central Register of Economic Units - CREU) • Does not include agricultural/government establishments • Contains 7,459 establishments (as at Jan 24, 2013)

  3. Establishment Classifications • Employment size (total number of persons employed) • Small - less than 10 employees (<10) • Medium – between 10 and 49 employees (10-49) • Large - 50 or more employees (50+) • Industry • In accordance with Jamaica Industrial Classification (JIC) 2005

  4. Common Characteristics- Sample Design • Single-stage selection • Only establishments are selected randomly • Stratification by industry, size, geography • Large/Monopoly establishments – all selected • Medium establishments selected randomly • Some medium establishments may be selected with certainty (i.e. purpose selection) in special circumstances • Probability Proportional to Size (PPS) sampling within strata

  5. Selection Criteria • Large establishments are selected with certainty • All establishments within industries with six (6) or less establishments are taken • All establishments which are engaged in specific activities of interest are taken • PPS sampling method used to take sample from among medium establishments • Measure of size: employment size

  6. Sample Size Formula n = sample sizez = 95% confidence levelp = population proportionq = 1 - pe = margin of error e.g. If z=95%, p=40%, e=3% Then n = [(1.96)2 * 0.4 * (1-0.4)] / (0.03)2 = 1024

  7. Apportioning Groups within Sample • Calculate sample size • Identify groups from which all units will be selected, and separate from sample and frame • Determine proportions of groups in reduced frame • Apportion remaining sample according to proportions in reduced frame

  8. Sample Allocation Example:

  9. Response Rates • Ever declining • Usually much less than those for household surveys • Over-sampling done to compensate for expected non-response • Non-responding establishments not replaced • Out-of-business establishments replaced with establishments of similar characteristics • Weighting using sampling fractions and non-response rates

  10. END

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