1. CHAPTER 4: Data Collection and Sampling Methods
to accompany
Introduction to Business Statistics
fourth edition, by Ronald M. Weiers
Presentation by Priscilla Chaffe-Stengel
Donald N. Stengel
© 2002 The Wadsworth Group

2. Chapter 4 - Learning Objectives
Describe the types of studies and their purposes:
Exploratory
Descriptive
Causal
Predictive
Explain the differences between data sources:
Primary
Secondary: Internal versus External
Differentiate between sampling designs:
Probabilitistic versus nonprobabilitistic designs
Differentiate between sampling and nonsampling errors.
© 2002 The Wadsworth Group

3. Chapter 4 - Key Terms Error Types of Studies Types of Data
Sampling
Nonsampling
Types of Studies
Exploratory
Descriptive
Causal
Predictive
Types of Data
Primary
Secondary
Internal vs External
Probability sample
Simple random sample
Systematic sample
Stratified sample
Cluster sample
Nonprobability sample
Convenience sample
Quota sample
Purposive sample
Judgment sample
© 2002 The Wadsworth Group

4. Types of Studies Exploratory Descriptive Causal Predictive
Understand a problem, identify relevant variables, formulate hypotheses
Descriptive
Establish reliable measurements
Causal
Determine relationships among variables
Predictive
Use analysis to forecast
© 2002 The Wadsworth Group

5. Sources of Data Primary Secondary
Data generated by the researcher for this study
Survey, experimental, observational research most popular
Tend to require more time and expense than secondary data
Secondary
Data gathered from another source or for another purpose
Internal sources within the researcher’s organization
External sources, including governmental, trade, commercial and internet sources
© 2002 The Wadsworth Group

6. Types and Sources of Error
Sampling Error
Random, nondirectional
When a sample is used instead of a census
Nonsampling Error
Directional bias overstating or understating the true population parameter
Potential sources:
Poor sample design
Poor measurement
Poor instrumentation
© 2002 The Wadsworth Group

7. Types of Samples Simple random Systematic
Probability, or Scientific, Samples: Each element to be sampled has a known (or calculable) chance of being selected.
Simple random
Systematic
Every person has an equal chance of being selected. Best when roster of the population exists.
Randomly enter a stream of elements and sample every kth element. Best when elements are randomly ordered, no cyclic variation.
© 2002 The Wadsworth Group

8. Types of Samples Stratified Cluster
Probability, or Scientific, Samples: Each element to be sampled has a known (or calculable) chance of being selected.
Stratified
Cluster
Randomly sample elements from every layer, or stratum, of the population. Best when elements within strata are homogeneous.
Randomly sample elements within some of the strata. Best when elements within strata are heterogeneous.
© 2002 The Wadsworth Group

9. Types of Samples Convenience Quota
Nonprobability Samples: Not every element has a chance to be sampled. Selection process usually involves subjectivity.
Convenience
Quota
Elements are sampled because of ease and availability.
Elements are sampled, but not randomly, from every layer, or stratum, of the population.
© 2002 The Wadsworth Group

10. Types of Samples Purposive Judgment
Nonprobability Samples: Not every element has a chance to be sampled. Selection process usually involves subjectivity.
Purposive
Judgment
Elements are sampled because they are atypical, not representative of the population.
Elements are sampled because the researcher believes the members are representative of the population.
© 2002 The Wadsworth Group

11. Example: Types of Data Problem 4.46
The Sonic Travel Agency has not kept pace with the current boom in family vacation air travel between the agency’s northern city and sunny Florida. For each of the following, indicate whether they are primary or secondary. If secondary, further indicate whether they are internal or external.
© 2002 The Wadsworth Group

12. Problem 4.46
a) Sonic’s research department conducts a survey of past customers to determine their level of satisfaction with the agency’s service
a) Primary data
The data were generated by the researcher to study this problem.
© 2002 The Wadsworth Group

13. Problem 4.46, continued
b) The Florida Bureau of Tourism sends travel agencies across the nation the results of a study describing the characteristics of winter vacationers to the state, including where and how long people intended to stay.
b) Secondary data
The data were not generated for the purpose of examining the question at hand.
External data
The data were provided by an outside agency, the Florida Bureau of Tourism.
© 2002 The Wadsworth Group

14. Problem 4.46, continued
c) To get a better grasp of the problem, the president of Sonic examines the company’s annual reports for the past ten years.
c) Secondary data
The data were not generated for the purpose of examining the problem at hand.
Internal data
The data were produced from within the firm, so they are internal data.
© 2002 The Wadsworth Group

15. Example: Types of Studies Problem 4.48
For each of the report titles below, indicate whether the study involved was exploratory, descriptive, causal, or predictive.
© 2002 The Wadsworth Group

16. Problem 4.48
a) “The Popularity of Bowling as a Participant Sport in Ohio.”
b) “The Effects of TV Violence on Crime in Small Towns.”
a) Descriptive study
This is probably a descriptive study showing the number of people who bowl in Ohio.
b) Causal study
This is probably a causal study that examines the effect of TV violence (the cause) on crimes in small towns (the outcomes).
© 2002 The Wadsworth Group

17. Problem 4.48, continued
c) “A Preliminary Investigation of the Market for Pet Foods.”
d) “Family Vacationing in the 21st Century.”
c) Exploratory study
This is probably an exploratory study that points out relationships and possible hypotheses for further study.
d) Predictive study
This is probably a predictive study to forecast vacationing patterns in the 21st century.
© 2002 The Wadsworth Group

18. Example: Types of Errors Problem 4.64
Researchers at a university with an enrollment of 12,000 take a census of the entire student population, asking: “Shoplifting is not only illegal, it raises the prices that we all have to pay. Have you ever shoplifted from the university bookstore?” Based on this, discuss the possible presence of a) sampling and b) nonsampling error.
© 2002 The Wadsworth Group

19. Problem 4.64 a) Sampling error not present
b) Nonsampling error present
a) Since the study includes the entire student population, there will be no sampling error present.
b) Because the question’s wording invites biased responses, students may be afraid to admit to shoplifting, so there will be nonsampling errors present.
© 2002 The Wadsworth Group