This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'In random sampling the chances of being picked up are: \nSelect and explain. \nA. same and unknown., B. same and known., C. different and unknown., D. different and known .', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sampling Methods:\nSimple random sampling — applicable when the population ¡s small, homogenous.\nIn random sampling chances of being picked up is SAME and KNOWN. Done by lottery method or, a table of random numbers.\n\nMultistage sampling — large country survey.\n\nMultistage sampling — sample procedure is carried out in several stages using simple random technique.\nONLY "MULTISTAGE"\xa0method.\nExamples - farmers in India may be grouped into various states, then into districts, then into talukas, further into villages within talukas and then farmers within villages.\n\nMultiphase- sampling done in different phases- e.g.- TB survey.\n\nSUBGROUP means ‘STRATA →. Mentioned in Stratified sampling.\nStratified sampling — used when population is heterogeneous.\nThe population under study is 1st divided into homogenous group/classes called strata and then the sample is drawn from each stratum at random in proportion to its size such as selecting sample from defined areas, classes, religions, ages or sexes.\n\n\nNATURAL HABITAT e.g.-village/region ) used in cluster sampling.\nCluster sampling — used when units of population are natural groups or clusters such as village, schools etc.\n— Both stratified and cluster is 2 stage sampling methods.\n— The main difference b/w them is that ¡n cluster sampling the cluster is treated as sampling unit so analysis is done on a population of cluster while in stratified sampling the analysis is done on elements within strata.\nThe main objective of cluster sampling is to reduce cost by increasing sample efficiency. This contrast with stratified sampling where the main objective is to INCREASE PRECISION.', 'role': 'assistant'}]