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Saturday, November 26, 2011

Introduction and Data Collection (PPT)

Basic Business Statistics 8th Edition
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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