For a survey a village is divided into 5 lanes then each lane is sampled randomly is an example is ?
Correct Answer: Systemic random sampling
Description: Ans. is 'c' i.e., Stratified random sampling Simple random sampling has been explained (See above explanation). Systematic random sampling In order to do systematic random sampling, the individuals in a population are arranged in a ceain way (for example, alphabetically). o A random staing point is selected and then every nth (for example 10th or 15th) individual is selected for the sample. o That is, after arranging the individuals in ceain pattern (e.g., alpabetically) a staing point is chosen at random, and choices thereafter at regular intervals. For example, suppose you want to sample 8 houses from a street of 120 houses. 120/8 = 15, So every 15th house is chosen after a random staing point between 1 and 15. If the random staing point is 11, then the houses selected are -4 11, 26, 41, 56, 71, 86, 101, and 116. o In contrast to simple random sampling, some houses have a larger selection probabily e.g., in this question 11, 26, 41, 56, 71, 86, 100 and 116. While the remaining number can not be selected. Stratified random sampling When sub-populations vary considerably, it is advantageous to sample each subpopulation (stratum) independently. o Stratification is the process of grouping members of the population into relative hemogenous subgroups before sampling. o The strata should be mutually exclusive, every element in the population must be assigned to only one stratum. o Then systematic random sampling method is applied within each stratum. Population Stratification -4 Systematic random sampling -4 Sample. o This often improves the representativeness of the sample by reducing sampling error. o For example, suppose in a population of 1000, sample of 100 is to be drawn for Hb estimation, first conve the population into homogenous striata (e.g., 700 males and 300 females), then draw 70 males and 30 females by doing systematic random sampling. Now see the question o First the village has been stratified into five lanes. o Then random sampling is done on each lane. o It is stratified random sampling. Multistage random sampling: o Is done in successive stages; each successive sampling unit is nested in the previous sampling unit o Advantage: Introduces flexibility in sampling. o For example, in large country surveys, states are chosen, then districts, then villages, then every 10th person in village as final sampling unit. Multiphase random sampling: Is done in successive phase; pa of information is obtained from whole sample and pa from the sub-sample. o For example, in a TB survey, Mantourx test done in first phase, then X-ray done in all Mantoux positive, then sputum examined in all those with positive X-ary findings.
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