NON -PROBABILITYSAMPLING

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Hello !!I am Arpit Surana

arpitsurana116116@gmail.com www.linkedin.com/in/arpitsurana116

NON – PROBABILITY SAMPLING

Non-probability sampling is a sampling technique where the odds of any member being selected for a sample cannot be calculated. It’s the opposite of probability sampling, where you can calculate the odds.

For example, one person could have a 10% chance of being selected and another person could have a 50% chance of being selected. It’s non-probability sampling when you can’t calculate the odds at all

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WHEN? WHY? TO USE NON-PROBABILITY SAMPLING

1. This type of sampling can be used when demonstrating that a particular trait exists in the population.

2. It can also be used when the researcher aims to do a qualitative, pilot or exploratory study.

3. It can be used when randomization is impossible like when the population is almost limitless.

4. It can be used when the research does not aim to generate results that will be used to create generalizations pertaining to the entire population.

5. It is also useful when the researcher has limited budget, time and workforce. 5

Advantages

Possibility to reflect the descriptive comments about the sample

Cost-effectiveness and time-effectiveness

Effective when it is unfeasible or impractical to conduct probability sampling

PRONS & CONS

Disadvantages

Unknown proportion i.e. lack of representation of the entire population

Lower level of generalization of research findings compared to probability sampling

Difficulties in estimating sampling variability and identifying possible bias

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Non-Probability Sampling

Conven-ience

sampling

Purposive sampling

Quota sampling

Snowball sampling

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CONVENIENCE SAMPLING

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1Also know as Accidental Sampling

“ In convenience sampling no inclusion criteria identified prior to the selection of subjects. The sample is selected in anyway for the sake of easiness and convenience

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EXAMPLES

▰ Facebook polls

▰ Pepsi Challenge

▰ Feedback system in big companies

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Advantages

Simplicity of sampling and the ease of research

Helpful for pilot studies and for hypothesis generation

Data collection can be done in short duration of time

Cheapest to implement

PRONS & CONS

Disadvantages

Highly vulnerable to selection bias and influences beyond the control of the researcher

High level of sampling error

Studies that use convenience sampling have little credibility due to reasons above

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PURPOSIVE SAMPLING

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2Also known as judgment, selective or subjective sampling

“ The researchers or experts obtain a representative sample by using a sound judgment, which will result in saving time and money

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EXAMPLES

▰ TV reporters stopping certain individuals on the street in order to ask their opinions about GST on insurance (this can be asked to only to an educated man).

▰ A study of importance of exposure in colleges (this can be asked to only those students who has experienced exposure in college).

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Advantages

Cost-effective and time-effective

Requires limited number of primary data sources

One of the most time-effective sampling methods available

PRONS & CONS

Disadvantages

Vulnerability to errors in judgment by researcher

Low level of reliability and high levels of bias.

Inability to generalize research findings

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QUOTASAMPLING

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3It has two types controlled and uncontrolled

“ A method of gathering representative data from a group to ensure that sample group represents certain features of the population chosen by the researcher.

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HOW TO PERFORM QUOTA SAMPLING

1. Dividing the population into specific groups

Virgin Media employees in the UK as the sampling frame need to be divided into the following five groups according to their cultural background:

European, Asian (India), Asian (China), Black (African) and Other

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2. Calculating a quota for each group

Suppose you take 30 representatives from each group making total of 150.

3. Determine specific condition(s) to be met and quota in each group

Both genders, males and females need to be represented equally i.e. 15 each.

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Advantages

Quota sampling is good when you are pressed for time, since primary data collection can be done in shorter time

This sampling method can save costs and time.

It can also be done in absence of sampling frame

PRONS & CONS

Disadvantages

We can’t calculate sampling error and the projection of the research findings

There is disproportionately represented in the final sample group

It may suffer from researcher incompetency and/or lack of experience

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2 TYPES QUOTA SAMPLING

Uncontrolled sampling, in this the researcher is free to choose sample group members according to his/her will.

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Controlled Uncontrolled

Controlled sampling involves introduction of certain restrictions in order to limit researcher’s choice of samples.

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SNOWBALLSAMPLING

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4Also known as cold-calling, chain, chain-referral, and referral sampling.

“ Snowball sampling is where research participants recruit other participants for a test or study. It is used where potential participants are hard to find

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INTERESING NAME !!

It’s called snowball sampling because (in theory) once you have the ball rolling, it picks up more “snow” along the way and becomes larger and larger.

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EXAMPLES

▰ A study on investigating cheating on exams

▰ Company that involves primary data collection from employees of that company.

▰ Mostly used in taking surveys with the help of questionnaire.

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3 PATTERNS OF SNOWBALL SAMPLING

Exponential non-discriminative snowball sampling

The first subject recruited to the sample group provides multiple referrals.

Exponential discriminative snowball sampling

Subjects give multiple referrals, however, only one new subject is recruited among them.

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Linear snowball sampling

Formation of a sample group starts with only one subject and the subject provides only one referral.

Advantages

The ability to recruit hidden populations

The possibility to collect primary data in low cost

It can be completed in a short duration of time

A very little planning is required to start sampling process

PRONS & CONS

Disadvantages

Oversampling can be done

Respondents may be hesitant to ask all questions

It is not possible to determine the actual pattern of distribution of population.

It is not possible to determine the sampling error 31

REFERENCES

https://research-methodology.net

http://www.statisticshowto.com

https://images.google.com/

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THANKS!Any questions?

Just comment me or you can find me at arpitsurana116116@gmail.com

www.linkedin.com/in/arpitsurana116/