Sampling: Design and Procedures

Presented byDr. Sunil Chauhan 4

Varun Jalan 14

Keith Mascarenhas 24

Krishna R 34

Jigar Shah 44

Adarsh Kumar 54

Some Definitions…• POPULATION: The aggregate of all the elements , sharing

some common set of characteristics , that comprises the universe for the purpose of the marketing research problem

• CENSUS: A complete enumeration of the elements of a population or study objects

• SAMPLE:A subgroup of the elements of the population selected for participation in the study

SAMPLE DESIGNING PROCESSDefine the target population

Determine the sampling frame

Determine the sample size

Select a sampling technique(s)

Execute the sampling process

So what are these steps??

1. DEFINE TARGET POPULATION: The collection of elements or objects that possess the information sought by the researcher and about which inferences are to be made

2. DETERMINE THE SAMPLING FRAME: A representation of the elements of the target population

Sample Designing Steps

3.SELECTING A SAMPLING TECHNIQUE:• Bayesian approach

• Sampling with replacement

• Sampling without replacement

Sample Designing Steps

4.DETERMINING THE SAMPLE SIZERefers to the number of elements to be included in the study

Some factors to be considered are:-a. Importanceb. Nature of researchc. Number of variablesd. Nature of analysise. Sample sizes usedf. Incidence /Completion ratesg. Resource constraints

Sample Designing Steps

5. EXECUTE THE SAMPLING PROCESS• Detailed specifications are required for every stage• Procedures should be specified for each stage and on how to

conduct the data collection• Contingency plans should be made in case of of non

availability of sampling unit

Why Sampling??

Some Advantages of sampling are:-

1. Economical and cheaper2. Faster to execute3. Practical in most situation4. Can give comprehensive

information5. Saves in time and money

Non probability Techniques

Non-probability Sampling

• Non probability sampling does not involve random selection• Accidental or Purposive

Non-probability techniques

Convenience Sampling

Judgemental Sampling

Quota Sampling

Snowball Sampling

Convenience Sampling

• ADVANTAGES– Easy access – Used in pilot studies

• DISADVANTAGES– Sampling bias, sample not representative– Poor external validity

SNOWBALL SAMPLING

• Linear Snowball Sampling

• Exponential Non-Discriminative Snowball Sampling

• Exponential Discriminative Snowball Sampling

• ADVANTAGES OF SNOWBALL SAMPLING– The chain referral process allows the researcher to reach

populations that are difficult to sample when using other sampling methods.

– Cheap, simple and cost-efficient.– Little planning and fewer workforce compared to

other sampling techniques

• DISADVANTAGES OF SNOWBALL SAMPLING– Little control over the sampling method– Representativeness of the sample is not guaranteed

JUDGMENTAL SAMPLING

• Involves selecting a group of people because they have particular traits that the researcher wants to study

• This type of sampling technique is also known as purposive sampling and authoritative sampling

• e.g. consumers of a particular product or service in some types of market research

• EXAMPLE OF JUDGMENTAL SAMPLINGIn a study wherein a researcher wants to know what it takes to graduate summa cum laude in college, the only people who can give the researcher first hand advise are the individuals who graduated summa cum laude. With this very specific and very limited pool of individuals that can be considered as a subject, the researcher must use judgmental sampling.

• WHEN TO USE JUDGMENTAL SAMPLING ??

• SETBACKS OF JUDGMENTAL SAMPLING.are with the authority and in the sampling process

• WHEN TO USE QUOTA SAMPLES

QUOTA SAMPLINGIn quota sampling the selection of the sample is made by the interviewer, who has been given quotas to fill from specified

sub-groups of the population.

STEP-BY-STEP QUOTA SAMPLING

EXAMPLE OF QUOTA SAMPLES• In a study wherein the researcher likes to compare the

academic performance of the different high school class levels, its relationship with gender and socioeconomic status, the researcher first identifies the subgroups.

• Usually, the subgroups are the characteristics or variables of the study. The researcher divides the entire population into class levels, intersected with gender and socioeconomic status. Then, he takes note of the proportions of these subgroups in the entire population and then samples each subgroup accordingly.

DISADVANTAGES OF QUOTA SAMPLES• Only the selected traits of the population were taken

into account in forming the subgroups

Probability Techniques

Probablity techniques

Simple Random Sampling

Systemic Sampling

Stratified Sampling

Disproportionate

Proportionate

Cluster Sampling Others

Simple Random Sampling

Simple random sampling is a method ofprobability sampling in which

every unit has an equal nonzero chance of being selected

Systematic Random Sampling

Systematic random sampling is a method of

probability sampling in which the defined

target population is ordered and the sample is selected

according to position using a skip interval

Steps in Drawing a Systematic Random Sample

• 1: Obtain a list of units that contains an acceptable frame of the target population

• 2: Determine the number of units in the list and the desired sample size

• 3: Compute the skip interval• 4: Determine a random start point• 5: Beginning at the start point, select the units by

choosing each unit that corresponds to the skip interval

Stratified Sampling

• Population divided into non-overlapping strata followed by random selection, random systemic selection

• Types – Proportionate and Disproportionate• Useful – for homogenous groups, to highlight a

specific strata, find relationship between two strata• Advantages – sample representative, biases reduced,

external validity, greater precision• Disadvantages – relevance of stratification variables,

cost, time

Cluster sampling

• Division of entire population into geographical clusters, followed by simple random, systemic random methods

• One stage & Two stage• Useful in case of homogenous population• Advantages – cheap, quick & easy• Disadvantages – sampling error in case of non-

homogenous population

Other Sampling Techniques

• Sequential Sampling

• Double Sampling

Conditions Favoring the Use of

Factors

Nonprobability sampling

Probability sampling

Nature of research

Exploratory

Conclusive

Relative magnitude of sampling and nonsampling errors

Nonsampling errors are larger

Sampling errors are larger

Variability in the population

Homogeneous (low)

Heterogeneous (high)

Statistical considerations

Unfavorable Favorable

Operational considerations Favorable Unfavorable

International Marketing Research• Differing Respondents

– US• Cereal:Children• Automobiles: Women

– Middle East• Automobiles: Men

• Accessibility– Unnumbered & unidentified streets/houses– Cultural norms

• Mexico• Saudi Arabia

• Sampling frame– Unavailability of information on target population

• Lack of census• Red tape

– Unavailable/inaccurate maps

International Marketing ResearchCase:Consumers feel that a purchase in accompanied by a degree of risk

Target Respondent:Upper middle-income woman residing in major city

Countries for comparison:US with Mexico, Netherlands, Turkey, Thailand & Saudi Arabia

Location Sampling Technique How?United States Random Sampling Telephone directory

Mexico Judgemental Sampling 1. Experts identified neighbourhoods2. Random selection

Thailand Judgemental Sampling Store intercept technique

Saudi Arabia Convenience Sampling Snowball Technique

Internet Applications Example: ITOCHU Corporation

• Launched Internet sampling service, February 14, 2011

• Sampling resources– Yahoo! Japan

• Yahoo Japan Corporation

– Famiport multimedia terminals installed in approximately 8,100 FamilyMart stores nationwide• FamilyMart Co., Ltd.

– Famima.com Co., Ltd.

ITOCHU Corporation• Features:

– Identifies sampling target Issues coupon IDs to the potential purchaser group that is being targeted by the provider of the product based on surveys to which consumers have responded on the “Premono” site in Yahoo! Japan

– Reduces sampling operating costs Coupon IDs are issued by e-mail and samples are handed over at FamilyMart stores, thus greatly reducing sampling operating costs such as distribution costs and labor costs.

– Gathers marketing data related to sampling Uses the “Premono” site in Yahoo! Japan to conduct preliminary and follow-up questionnaire surveys of sampling targets, thereby providing effective marketing data to the provider of the product

ITOCHU Corporation

Thank You