PPT By : Sampling Methods Murali.sc

5/27/12 5/27/12

PPT BY Murali Sc & PPT BY Murali Sc & Team...

11

1

SamplingSampling : its the process of learning about the population on the basis of a sample drawn

Sampling Methods Sampling methods: are used to select a sample from within a general population. 5/27/12 PPT BY Murali Sc & 22

Sampling Methods:Probability & Non-probability sampling

1. Meaning of Probability sampling : are those inwhich every item in the universe has chance of being chosen from the sampling. Eg N = (sample size) Number of units in the :population from 1 to N decide on the N(sample size) that you want or need. k = N/n = the interval size .

5/27/12

PPT BY Murali Sc &

33

2. Meaning of Non-probability sampling :A sample of units where the selected units in the sample have an unknown probability of being selected and where some units of the target population may even have no chance at all of being selected or being in the sample.

Non-probability sampling does not involve random selection as shown in figureNon-probability samples may or may not represent the population well, and it will often be hard for us to know how well we've done so.

5/27/12

PPT BY Murali Sc &

44

Probability sampling Consists of : 1. Simple random sampling :

Simple random sampling refers to sampling technique in which each & every units of the population has an equal opportunity selected & 5/27/12 of being PPT BY Murali Sc in the sample. 55

2. Stratified random sampling :Stratified sampling technique wherein the researcher divides the entire population into different subgroups The population is subdivided into same kind of groups on basis of: or Age, Gender, Socio-economic Status, Religion, Nationality and Educational.

5/27/12

PPT BY Murali Sc &

66

3. Systematic sampling :its the researcher first randomly picks the first item or subject from the population. Then, the researcher will select each not subject from the list.

The procedure involved in systematic random sampling is very easy and can be done manually. The results are representative of the population unless certain characteristics of the population are repeated for every not individual, which is highly unlikely. 5/27/12 PPT BY Murali Sc & 77

4.Cluster sampling :under this technique, the total population is divided into groups (or clusters) and a simple random sample of the groups is selected.

A common motivation for cluster sampling is to reduce the average cost per interview. Given a fixed budget, this can allow in increased sample size.5/27/12 PPT BY Murali Sc & 88

5. Sequential sampling:

Sequential sampling is a non-probability sampling technique wherein the researcher picks a single or a group in a given time interval, conducts his study, analyzes the results then picks another group of subjects if needed is said to be as sequential sampling.

5/27/12

PPT BY Murali Sc &

99

6.Multi-stage samplingIs a sampling method in which the population is divided into a number of groups or primary stages from which samples are drawn; these are then divided into groups or secondary stages from which samples are drawn.

5/27/12

PPT BY Murali Sc &

1010

Non-probability sampling Consists of : 1. Convenience or accidental sampling

sample being drawn from that part of the population which is close to hand. That is, a sample population selected because it is readily available and convenient. Its obtained by selecting is obtained by selecting convenient population unit, Convenience sampling refers to that fraction of the population being investigated which is selected neither by probability nor by judgement but by convenenience.

5/27/12

PPT BY Murali Sc &

1111

2. Quota sampling :In quota sampling, a population is first segmented into mutually exclusive sub-groups, just like stratified sampling. its the most commonly used sampling technique In a quote sampling, quotas are set up according to specified characteristics such as ~ income, Age, Gender, Socio-economic Status, Religion, Nationality and Educational ~

The main difference between the quota and stratified sampling is:the researcher has control over who will be in the sample (he can contact certain people and include them in the sample). Stratified sampling : the researcher can not select the individuals to be included in the sample (he doesn't have control over who will be in the simple).

quota sampling :

5/27/12

PPT BY Murali Sc &

1212

3. judgment sampling :is a type of non-random sample, which is selected based on the opinion of an expert. Results obtained from a judgment sample are subject to some degree of bias (preference), due to the frame and population not being identical. The disadvantage : of this is that it uses people's judgment. This is bad because people's judgment is poor.

The frame is a list of all the units, items, people, etc that define the population to be studied. 5/27/12 PPT BY Murali Sc & 1313

4. Snow-ball sampling or chain sampling

Snowball Sampling : is technique of building up a list or a sample of special population by using an initial set of its members as information A popular term for a method used to obtain subjects for a study in which the initial cohort is small; in SS, participants are asked to name acquaintances who might be willing to participate in the study 5/27/12 PPT BY Murali Sc & 1414

Steps in Sampling:5 steps which precede collection of data by means of sample. 1.Defining the P. or Universe: P. is specific group which Research wish to study & plan to generalize the results.

2.Development of a frame: A frame is a list of population. It consists of names & addresses of the individuals & Institutions. It can also specify a definite location, boundary, set of rules by 5/27/12 PPT BY Murali Sc & which S. unit can be identified.

3.Selection of Sample Design:Research Can go for probability or Non-Probability design. If the Research. Wants to estimate the S. error of the results, the Probability sample should be used.

4.Selecting the S. size:Sample size should never be less than 30. Sample Size should be around onetenth of the size of the Population proper size depends on Requirements.

5.Selection of substitute sampling is units & Cost consideration:Substitute of Sampling is necessary. Size & type of Sampling & data collection method depend upon cost considerations 5/27/12 PPT BY Murali Sc &

1616

5/27/12

PPT BY Murali Sc &

1717