Chapter 1 - Introduction and Data Collection
Chapter Topics
- Why a manager needs to know about statistics
- The growth and development of modern statistics
- Key definitions
- Descriptive versus inferential statistics
Chapter Topics
Why data are needed
- Types of data and their sources
- Design of survey research
- Types of sampling methods
- Types of survey errors
Why a Manager Needs to Know about Statistics
- To know how to properly present information
- To know how to draw conclusions about populations based on sample information
- To know how to improve processes
- To know how to obtain reliable forecasts
The Growth and Development of Modern Statistics Key Definitions
- A population (universe) is the collection of things under consideration
- A sample is a portion of the population selected for analysis
- A parameter is a summary measure computed to describe a characteristic of the population
- A statistic is a summary measure computed to describe a characteristic of the sample
Population and Sample
Statistical Methods
Descriptive statistics
Collecting and describing data
Inferential statistics
Drawing conclusions and/or making decisions concerning a population based only on sample data
Descriptive Statistics
Collect data
e.g. Survey
Present data
e.g. Tables and graphs
Characterize data
e.g. Sample mean =
Inferential Statistics Estimation
- e.g.: Estimate the population mean weight using the sample mean weight Hypothesis testing
- e.g.: Test the claim that the population mean weight is 120 pounds
Why We Need Data
- To provide input to survey
- To provide input to study
- To measure performance of service or production process
- To evaluate conformance to standards
- To assist in formulating alternative courses of action
- To satisfy curiosity
Data Sources Types of Data Design of Survey Research
- Choose an appropriate mode of response
- Reliable primary modes
- Personal interview
- Telephone interview
- Mail survey
- Less reliable self-selection modes (not appropriate for making inferences about the population)
- Television survey
- Internet survey
- Printed survey on newspapers and magazines
- Product or service questionnaires
Design of Survey Research
- Identify broad categories
- List complete and non-overlapping categories that reflect the theme
- Formulate accurate questions
- Make questions clear and unambiguous. Use universally-accepted definitions
- Test the survey
- Pilot test the survey on a small group of participants to assess clarity and length
Design of Survey Research
- Write a cover letter
- State the goal and purpose of the survey
- Explain the importance of a response
- Provide assurance of respondent’s anonymity
- Offer incentive gift for respondent participation
Reasons for Drawing a Sample
- Less time consuming than a census
- Less costly to administer than a census
- Less cumbersome and more practical to administer than a census of the targeted population
Types of Sampling Methods
- Probability Sampling
- Subjects of the sample are chosen based on known probabilities
Simple Random Samples
- Every individual or item from the frame has an equal chance of being selected
- Selection may be with replacement or without replacement
- Samples obtained from table of random numbers or computer random number generators
Systematic Samples
- Decide on sample size: n
- Divide frame of N individuals into groups of k individuals: k=n/n
- Randomly select one individual from the 1st group
- Select every k-th individual thereafter
Stratified Samples
- Population divided into two or more groups according to some common characteristic
- Simple random sample selected from each group
- The two or more samples are combined into one
Cluster Samples
- Population divided into several “clusters,” each representative of the population
- Simple random sample selected from each
- The samples are combined into one
Advantages and Disadvantages
- Simple random sample and systematic sample
- Simple to use
- May not be a good representation of the population’s underlying characteristics
- Stratified sample
- Ensures representation of individuals across the entire population
- Cluster sample
- More cost effective
- Less efficient (need larger sample to acquire the same level of precision)
Evaluating Survey Worthiness
- What is the purpose of the survey?
- Is the survey based on a probability sample?
- Coverage error – appropriate frame
- Nonresponse error – follow up
- Measurement error – good questions elicit good responses
- Sampling error – always exists
Types of Survey Errors
- Coverage error
- Non response error
- Sampling error
- Measurement error
Chapter Summary
- Addressed why a manager needs to know about statistics
- Discussed the growth and development of modern statistics
- Addressed the notion of descriptive versus inferential statistics
- Discussed the importance of data
Chapter Summary
- Defined and described the different types of data and sources
- Discussed the design of survey
- Discussed types of sampling methods
- Described different types of survey errors
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