In random sampling the chances of being picked up are:
Sampling Methods:
Simple random sampling — applicable when the population ¡s small, homogenous.
In random sampling chances of being picked up is SAME and KNOWN. Done by lottery method or, a table of random numbers.

Multistage sampling — large country survey.

Multistage sampling — sample procedure is carried out in several stages using simple random technique.
ONLY "MULTISTAGE" method.
Examples - 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.

Multiphase- sampling done in different phases- e.g.- TB survey.

SUBGROUP means ‘STRATA →. Mentioned in Stratified sampling.
Stratified sampling — used when population is heterogeneous.
The 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.


NATURAL HABITAT e.g.-village/region ) used in cluster sampling.
Cluster sampling — used when units of population are natural groups or clusters such as village, schools etc.
— Both stratified and cluster is 2 stage sampling methods.
— 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.
The 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.
same and unknown.
same and known.
different and unknown.
different and known .