Sampling Methods

Date : 4.05.2020 
Sub  : Economics
Day  : 1
Time : 8:20am -9am and 10:45am- 11:25
Period : 2 and 5 
Class    : 11

Learning Outcomes

• Mehods of Sampling
• Methods used in daily life
• Stdents come to find out which is the most commonly used method of Sampling

A very good morning students 

Thank you for logging in

We had started our third chapter in Statistics .So far we have learnt what is Census and Sampling.

Today we will be learning the Methods of Sampling

Please go through the notes carefully.

The methods of Sampling have been explained.

For class 11 syllabus  we shall restrict ourselves to only this much.

METHODS OF SAMPLING :
          A. RANDOM SAMPLING ( it is called random sampling when every item in the population has an equal possibility/ probability of being selected) There are three kinds:

·          Simple/ probability random sampling

·         Stratified random sampling

·         Systematic / quasi random samplin

B. NON RANDOM SAMPLING (It is called non-random sampling because at the very outset, every item/person does not have an equal chance of getting selected as part of the sample).The two kinds of non-random sampling are
                                     *Judgement/ deliberate/Purposive non random sampling
                                     *Convenience non random sampling                                     

  A. RANDOM SAMPLING  METHODS:

1. SIMPLE/ PROBABILITY RANDOM SAMPLING

In this case, each individual unit has an equal probability of getting selected in the sample. It is 

free from judgement and discrimination as the sample is chosen at random, without any bias and 

prejudice.               

Eg: lottery method.

2. STRATIFIED RANDOM SAMPLING

# This method is useful only when the population of enquiry is heterogeneous (i.e. not identical).

# The universe is divided into strata (layers) or homogeneous groups (bearing similar qualities or features).

# An equal sample is chosen at random from each stratum/group/layer.

# Eg1. If a sample needs to be collected to study data regarding pocket money received by students of various age groups, the population is first divided into groups according to age and then, an equal representation/sample is chosen from each group.

 

  3. SYSTEMATIC / QUASI RANDOM SAMPLING
# This method is useful when a complete list of the population is available.
# A list of the population is prepared in some random order eg. Alphabetical order, height order, etc
# Every ‘n’th term is selected from the list, where
      n = POPULATION SIZE    =    200     =   20
                   SAMPLE SIZE                10
# Eg. If the size of the population is 200 units and the required sample size is 10, the value of ‘n’ is 20    (i.e. n= 200/10)
Consider 200 students in class 11. Each boy is given a number. Now, pick any number at random between 1 and 20 (because n=20) . Thereafter, every successive 20th value will be chosen. Say the first number chosen is 3, then the successive 23rd, 43rd, 63^rd, 83^rd, 103^rd, 123^rd, 143^rd, 163^rd and finally the 183rd value will be chosen. This automatically leads to a selection of 10 students.

   B) NON RANDOM SAMPLING

1. JUDGEMENT/ DELIBERATE/ PURPOSIVE NON RANDOM SAMPLINGIn this method, the investigator consciously chooses a sample using his judgement ( based on his prior experience, knowledge, preconceived notions).
There is a bias or prejudice involved in the choice. Thus, individual units do not have an equal probability of being selected.
Eg1. While choosing boys as members of the Editorial Board, the teacher concerned will choose only those boys who have the required skill set, thus resorting to judgement sampling.

2. CONVENIENCE NON RANDOM SAMPLINGIn this case, the selection of the sample is done on the basis of whatever is convenient to the investigator/ enumerator.

Eg.1. If a teacher has to pick a sample of students from classes 11 and 12 to organise a party, she would probably find it most convenient to choose the sample from the sections that she teaches.

Please go through the  video link provided to you

Please ignore the methods that are not in the syllabus

https://www.youtube.com/watch?v=DWK54DbK7WQ

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