Inference Pandurang Vasudeo Sukhatme (July , - January , ) Learning Objectives After studying this chapter students are able to understand sampling techniques random sampling simple random sampling stratified random sampling systematic sampling sampling and non-sampling errors sampling distribution statistical inference estimation test of statistical hypothesis . Sampling Sampling is the procedure or process of selecting a sample from a population. Sampling is quite often used in our day-to-day practical life. XII Std - Business Maths & Stat EM Chapter - - .
. Basic concepts of sampling Population The group of individuals considered under study is called as population. The word population here refers not only to people but to all items that have been chosen for the study. Thus in statistics, population can be number of bikes manufactured in a day or week or month, number of cars manufactured in a day or week or month, number of fans, TVs, chalk pieces, people, students, girls, boys, any manufacturing products, etc… Finite and infinite population: When the number of observations/ individuals/products is countable in a group, then it is a finite population.
Example: weights of students of class XII in a school. When the number of observations/ individuals/products is uncountable in a group, then it is an infinite population. Example: number of grains in a sack, number of germs in the body of a sick patient. Sample and sample size A selection of a group of individuals from a population in such a way that it represents the population is called as sample and the number of individuals included in a sample is called the sample size.
Parameter and statistic Parameter: The statistical constants of the population like mean ( m ), variance( s ) are referred as population parameters. Statistic : Any statistical measure computed from sample is known as statistic. In practice, the parameter values are not known and their estimates based on the sample values are generally used. Note Types of sampling The technique or method of selecting a sample is of fundamental importance in the theory of sampling and usually depends