Marketing 6 Chapter 14Sampling Fundamentals Reported by: Franklin K. Go Raymond A. Gonzales Angelo R. Cantor
Learning Objectives1. Distinguish between a census and a sample.2. Know the difference between sampling and non-sampling errors.3. Learn the concept of sampling process.4. Describe probability and non-probability sampling procedures.5. Determine sample size with ad-hoc methods.6. Learn to deal with non-response problems.7. Understand sampling in international context.
Sample or Census• A researcher is interested in the characteristics of the population wherein his potential target market may reside. The respondents are asked to input necessary information through surveys called census.
When a Census is Appropriate• A census is appropriate if the sample size is small. Every individual may be included in the population.
When a Sample is Appropriate• A sample is appropriate if the population is large, the time allotted in obtaining the information from the population is long and the cost is high.
Error in SamplingError in sampling occurs if there is a gap between the true value and the observed value of the variable interest of the population.• Sampling Error occurs if the error lies in the sample parameter and the sample statistics because of sampling.• Non-sampling Error occurs if the error lies in the population.
Sample ProcessFactors that should be considered when the decision to use a sample is made:• Various steps included in sampling• Major activities with sampling process
Various steps included in sampling
Major activities with sampling process1. Identify the target population.2. Determine the sampling frame.3. Resolving the Differences.4. Selecting a sampling procedure.5. Determining the relevant sample size.6. Obtaining information from respondents.7. Dealing with the non-response public.8. Generating information for decision-making purposes.
Determining the Target PopulationThe following should be considered in determining the target population:1. Look to the research objectives2. Consider alternatives3. Know your market4. Consider the appropriate sampling unit5. Specify clearly what is excluded6. Don’t overdefine7. Should be reproducible8. Consider convenience
Determining the Sampling FrameTasks to do in determining the sample frame:1. Create lists2. Create lists for telephone interviewing3. Dealing with population sampling frame difference
Determining the Sampling FrameThree types of problems when dealing with population sampling frame difference:1. Subset problem2. Superset problem3. Intersection problem
Selecting a Sampling Procedure• Select between Bayesian Sampling Procedure and Traditional Sampling Procedure.• Decide whether the sample may have a replacement or not.
Probability SamplingProbability sampling involves four considerations:1. The target population must be specified.2. The methods for selecting sample needs to be developed.3. The sample size must be determined.4. The non-response problem must be addressed.
Selecting the Probability SampleMethods used to select a probability sample:• Simple Random Sampling• Accuracy Cost Trade-off• Stratified Sampling• Proportional Stratified Sampling• Directly Proportional Stratified Sampling• Inversely Proportional Stratified Sampling• Disproportional Stratified Sampling• Cluster Sampling• Systematic Sampling
Multistage Design Cities in Ajax Country City Population Cumulative Population Concorde 15000 1-15000Mountain View 10000 15001-25000 Filmore 60000 25001-85000 Austin 5000 85001-90000 Cooper 2000 90001-92000 Douglas 5000 92001-97000 Rural Area 3000 97001-100000
Non-probability SamplingThe following are stages where non- probability sampling is used: 1. Exploratory stage of a research project 2. Pretesting a questionnaire 3. Dealing with homogeneous population 4. When researcher lacks statistical knowledge 5. When operational ease is required
Non-probability SamplingThe following are the four types of non- probability sampling:1. Judgment2. Snowball3. Convenience4. Quota
Determining the Sample SizeHow large should the sample be?
Non-response ProblemsThe following are reasons why some of the populations become non-respondents:1. Refuse to respond2. Lack of ability to respond3. Not at home4. Inaccessible
What can be done about the non- response problems?1. Improve the research design to reduce non-responses.2. Repeat the contact one or more times to reduce non-responses (callbacks).3. Attempt to estimate the non-response bias.
Shopping Center SamplingShoppers are intercepted and interviewed personally or through surveys. This method is called store-intercept interviews.
Shopping Center SamplingShopping Center Selection• Selecting a shopping center is essential because the respondents will be those who live in the nearby area. The standard of living of the neighborhood will affect how the sampling will take place and the types of samples that will be obtained.
Shopping Center SamplingSample Locations within a Center• This is randomly selecting samples through shopping center visits.
Shopping Center SamplingTime Sampling• Time segments are devised when obtaining sample data because of the fact that the time people go shopping vary from one another.
Shopping Center SamplingSampling People versus Shopping Visits• Researchers should ask the respondents on how often they shop. The respondents are weighted based on the frequency of visits when getting the average.