Therefore the selected random numbers are (ii) Stratified Random Sampling Definition . In stratified random sampling, first divide the population into sub-populations, which are called strata. Then, the samples are selected from each of the strata through random techniques.The collection of all the samples from all strata gives the stratified random samples. When the population is heterogeneous or different segments or groups with respect to the variable or characteristic under study, then Stratified Random Sampling method is studied.
First, the population is divided into homogeneous number of sub-groups or strata before the sample is drawn. A sample is drawn from each stratum at random. Following steps are involved for selecting a random sample in a stratified random sampling method. (a) The population is divided into different classes so that each stratum will consist of more or less homogeneous elements.
The strata are so designed that they do not overlap each other. (b) After the population is stratified, a sample of a specified size is drawn at random from each stratum using Lottery Method or Table of Random Number Method. Stratified random sampling is applied in the field of the different legislative areas as strata in election polling, division of districts (strata) in a state etc… Example . From the following data, select random samples from the populationof heterogeneous group with size of through stratified random sampling, considering the following categories as strata.
Category1: Lower income class - % Category2: Middle income class - % Category3: Upper income class- % XII Std - Business Maths & Stat EM Chapter - - Solution Stratum Homogenous group Percentage from