COMPILED BY:MALVIKA – MBA BIOTECH – 11RASHMI – MBA BIOTECH - 12

OUTLINE SAMPLING. SAMPLING PROCESS. SAMPLING TYPES. SAMPLING ERROR.SAMPLE SIZE.

OUTLINE SAMPLING. SAMPLING PROCESS. SAMPLING TYPES. SAMPLING ERROR.SAMPLE SIZE.

The process of obtaining information from a sample of a larger group (population).

A sample is “a smaller (but hopefully representative) collection of units from a population used to determine truths about that population”.

SAMPLING BREAKDOWN

Characteristics of Good Samples :

Representative

Accessible

Low cost

OUTLINE

SAMPLING. SAMPLING PROCESS. SAMPLING TYPES. SAMPLING ERROR.SAMPLE SIZE.

1. Define the population :

The Element ...... individualsfamiliesseminar groups

Sampling Unit…. individuals over 20families with 2 kidsseminar groups at ”new”

university

Extent ............ individuals who have bought “one”

families who eat fast foodseminar groups doing

MR

Timing ......... bought over the last seven days

2. Identify the sampling frame :

Select “sample units” Individuals

Household

Streets

Telephone numbers

Companies

3. Select a sampling design or procedure :

PROBABILITY NON- PROBABILITY

4. Determine the sample size.

5. Draw the sample.

OUTLINE

SAMPLING. SAMPLING PROCESS. SAMPLING TYPES. SAMPLING ERROR.SAMPLE SIZE.

Probability sampling - equal chance of being included in the sample (random)

-simple random sampling

-systematic sampling

-stratified sampling

-cluster samplingNon-probability sampling - unequal chance of being included in the sample (non-random)

-convenience sampling

-judgment sampling

-snowball sampling

-quota sampling

PROBABILITY SAMPLING

SIMPLE RANDOM SAMPLING

A sampling procedure in which every element in the population has a known and equal chance of being selected as a subject (e.g., drawing names out of a hat).

SYSTEMATIC SAMPLING

If a sample size of n is desired from a population containing N elements, we might sample one element for every n/N elements in the population.

STRATIFIED SAMPLING

Population is divided on the basis of characteristic of interest in the population e.g. male and female may have different consumption patterns.

Cluster or Area Random Sampling

Clusters of population units are selected at random by dividing the population into clusters (usually along geographic boundaries) and then all or some randomly chosen units in the selected clusters are studied.

NON - PROBABILITY

SAMPLING

CONVENIENCE SAMPLINGSometimes known as grab or

opportunity sampling or accidental or haphazard sampling.

A type of non probability sampling which involves the sample being drawn from that part of the population which is close to hand. That is, readily available and convenient.

The researcher chooses the sample based on who they think would be appropriate for the study.

This is used primarily when there is a limited number of people that have expertise in the area being researched.

JUDGMENTAL SAMPLING

SNOWBALL SAMPLING

Selection of additional respondents is based on referrals from the initial respondents.

- friends of friends Used to sample from low incidence or rare populations.

Quota sampling is a method for selecting survey participants.

In quota sampling, a population is first segmented into mutually exclusive sub-groups, just as in stratified sampling.

Then judgment is used to select the subjects or units from each segment based on a specified proportion.

For example, an interviewer may be told to sample 200 females and 300 males between the age of 45 and 60.

This means that individuals can put a demand on who they want to sample (targeting).

QUOTA SAMPLING

OUTLINE

SAMPLING. SAMPLING PROCESS. SAMPLING TYPES. SAMPLING ERROR.SAMPLE SIZE.

Random Sampling Error

Random error- the sample selected is not representative of the population due to chance.

The level of it is controlled by sample size.

A larger sample size leads to a smaller sampling error.

Non-sampling Error

Systematic Error

The level of it is not controlled by sample size.

A response or data error is any systematic bias that occurs during data collection, analysis or interpretation, like:

Respondent error (e.g., lying, forgetting, etc.).

Interviewer bias.

Recording errors.

Poorly designed questionnaires.

The basic types of non-sampling error :

A non-response error occurs when units selected as part of the sampling procedure do not respond in whole or in part .

Non-probability sampling is less time consuming and less expensive.

The probability of selecting one element over another is not known and therefore the estimates cannot be projected to the population with any specified level of confidence.

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OUTLINE

SAMPLING. SAMPLING PROCESS. SAMPLING TYPES. SAMPLING ERROR.SAMPLE SIZE.

Size of sample should be determined by a researcher keeping in view:

1. Nature of universe: homo (small sample) hetero (large

sample).

2. No. of classes proposed: directly proportional to the sample size .

3. Nature of study: general (large) intensive (small).

4.Type of sampling: small random sample is better than a large but bad one.

5. Standard of accuracy: high level of

precision large sample.

6. Availability of finance: sample size =amount of money available.

7. Other considerations: size of population, size of

questionnaire, nature of

units, conditions.

www.socialresearchmethods.net/kb/sampling.phpen.wikipedia.org/wiki/Sampling_(statistics)psychology.ucdavis.edu/sommerb/.../

sampling/types.htmwww.investopedia.com/terms/s/samplingerror.asp

www.slideshare.net/dfmoore/sampling-sizeResearch Methodology - C.R.Kothari.

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