Probability proportional to size pps sampling includes a number of sample selection methods in which the probability of selection for a sampling unit is directly proportional to a size measure xit which is known for all sampling units and thought to be approximately proportional to the unknown f. A design effect coefficient of 1 0 means the sampling design is equivalent to simple random sampling.
To estimate the design effect an estimate of either.
Pps sampling and design effect. Consider a survey of 300 people which concludes that 50 of people agree with some statement or other. The design effect is basically the ratio of the actual variance under the sampling method actually used to the variance computed under the assumption of simple random sampling4 5 6. Salganik abstract hidden populations such as injection drug users and sex workers are central to a number of public health problems.
The deff is a measure that compares the ratios of sampling variance from the actual stratified cluster survey sample mics3 in the present case to a simple random. The inherent difference between simple random sampling and pps sampling is that in the former method the probability of drawing any specified unit at any given draw is the same. Variance estimation design effects and sample size calculations for respondent driven sampling matthew j.
Its effect can be assessed by the so called sample design effect or deff. The design effect often called just deff quantifies the extent to which the expected sampling error in a survey departs from the sampling error that can be expected under simple random sampling. Household sample surveys in developing and transition countries 127 c.
The loss of effectiveness by the use of cluster sampling instead of simple random sampling is the design effect. Follows from the use of pps sampling and is the preferred approach from a logistical and analytical point of view. In contrast in the latter method the probability differs from draw to draw.
Designing and selecting the sample 4 3 the choice of the cluster size is another parameter that has to be taken into account in determining sample size. The variance of the estimated proportion. A design effect greater than 1 0 means the sampling design reduces precision of estimate compared to simple random sampling cluster sampling for instance reduces precision.
The xi must all be strictly greater than 0. The design effects d2 y for a selection of estimates from each survey are shown in tables vii 2 through vii 6 for a description on how the design effect is calculated see chap. However because of the nature of these.
7 1 assembling design components 281 7 2 sampling weights 285 7 3 estimating a distribution function 288 7 4 plotting data from a complex survey 294 7 5 design effects 309 7 6 the national crime victimization survey 312 7 7 sampling and design of experiments 317 7 8 chapter summary 319 7 9 exercises 320 chapter 8 nonresponse 329 8 1 effects of. Design effect correction to sample size calculation due to cluster sample survey design.