Page 1 : 202°, , TABLE 8.1 Brief Review of Probability Sampling Techniques, Advantages, , Types with Description, , 1. Simple random, , _sampling:, “Every member of _, population has an_, equal chance of being, selected as subject” ~, , 2. Stratified random, ‘sampling:, “Dividing heteroge-_, , jeous population in_, strata based on selected traits, such as, age, gender, habitat,, and then random selection of sample from, each strata”, , 3. Systematic random, , sampling:, “Selecting of every Kt, , from the group,, such as eve:, , OS el, eae erery 100th, person’, , , , , , , , , , , , 4. Cluster or multistage, , y very large popula, , , Be PORUUATION Cee, , Prerequisites and Uses, , - Population should be, homogeneous, , - Must have list of the, elements/members, of the accessible, population, , - Random selection, , either by lottery,, , random table, or, , computer, , - Used for heterogeneous population, , - Division of hetefogeneous population in, strata based on selected traits, such as, age, gender, religion,, Socio-economic status,, diagnosis, education,, geographical region,, etc. ;, , - List of the target., population must be, available :, , - Random distribution, subjects rather than, segregation i, , - The first subject, number is chosen by, the help of random, number table, , - When population is, very large, such as in, ‘Asia’ random selection of geographic, clusters, , - Random selection of, subjects from selected, clusters ssi‘, , ~ Sample size is not, , fixed continue till inferences ae drawn, , , , sample in heteroge, Disadvantages, , , , , , - Needs up-to-date, complete list of all the, members of the Popu., lation, , - Expensive and time, consuming,, , Most reliable and, ‘jnbiased method, ‘Requires minimum, knowledge of study, population, , Free from sampling, errors /bias, , , , Ensures representative - Requires complete in., formation of population, , - Large population is, required, , - Chances of faulty clasgjfication of strata, , neous population, Comparison is possible in two groups, , - Less-representative, sample if subjects, are nonrandomly, distributed, , - Sometimes may result, in biased sample, , Convenient and simple to carry out, Distribution of sample, over entire population, , Cheap, quick, and - Possibility of high, , easy for a large popu- sampling error, _lation - Chances of least repre", Population parameters sentative sample due to, of population can be over-represented or, estimated for sample under-represented, Size cluster, , - Not possible to study #, phenomenon, which, needs to be studied one, point of time, , - Requires the repe, entry into the field to, collect the sample, , Study on best-possible, smallest sample, , Facilitates inferences, Bs ated