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QMM 280. Introduction to Statistics. Dr. Barry A. Wray Associate Professor Department of IS and OM. Introduction. What is a definition for statistics?

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qmm 280

QMM 280

Introduction to Statistics

Dr. Barry A. Wray

Associate Professor

Department of IS and OM

introduction
Introduction
  • What is a definition for statistics?
    • The field of Statistics is concerned with the collection, presentation, and analysis of data in order to assist a manager in the decisions making process.
  • What is the “story” of the data?
two main branches of statistics
Two Main Branches of Statistics

Descriptive

Inferential

Infer or make conclusions from an analysis of the data

  • Describe the data
  • Central Tendency
  • Dispersion
  • Distribution
sources of data
Sources of Data
  • Survey Data
  • Historical Records
  • Published Data
  • Manufacturing Data
  • Sales Data
types of data
TYPES OF DATA
  • QUALITATIVE
    • Data which is non numerical
  • QUANTITATIVE (Continuous)
    • Data which is numerical in nature
qualitative
QUALITATIVE
  • NOMINAL
    • Data classified into categories with no order implied
    • What color are your eyes?
    • What is your Occupation?
      • Accountant
      • Economist
      • Manager
      • Teacher
      • Unemployed (Student)
  • ORDINAL
    • Categorical data with ordering implied
    • How was the movie last night?
      • Excellent
      • Very Good
      • Good
      • Fair
      • Poor
quantitative continuous
QUANTITATIVE (Continuous)
  • Discrete
    • Usually integer values
      • Number of people
      • Number of defective items
  • Continuous
    • Fractional values
      • Weight
      • Age
      • Height
      • Time
types of data1
Types of Data
  • Time Series Data is data collected through time.
    • Stock prices are an example of time series data. Tomorrow’s starting price for a stock depends on the ending price of that stock today. Stock prices “move” over time so it is important to factor in this effect.
  • Cross Sectional Data does not have a “time” component
    • Data collected on a variable at a single point in time. For example you might be interested in doing a study of comparative housing prices for the 8 major cities in June 2000.
examining the data
Examining the Data
  • First step in any analysis is to examine the data
    • Arrays
      • Listing the data in ascending or descending order.
      • Useful in identifying common or outlying values
    • Tables
      • Summarizing the data into categories
      • Useful for visualizing important characteristics of the data
      • Frequency Distributions
    • Graphical Representations
      • Pie and Bar Charts
      • Histograms
descriptive measures
Descriptive Measures
  • Central Tendency
    • Mean
    • Median
    • Mode
  • Dispersion
    • Range
    • Mean Absolute Deviation
    • Standard Deviation
statistical terminology
Statistical Terminology
  • Population – the collection of ALL entities possessing some characteristic we are interested in.
  • Sample – some subset of a Population
  • Population Parameter – a summary measure of some characteristic we are interested in for all entities in a population.
  • sample statistic – a summary measure computed from a sample and used to estimate a Parameter from the Population where the sample was derived from.
selecting a sample
Selecting a sample
  • Why sample?
    • Cost and time advantages
    • Population size - Census too cumbersome
    • Destructive sampling
simple random sampling srs
simple random sampling (srs)
  • Definition
    • Each member of the population has an equally likely chance of being selected.
  • sampling with replacement
  • Basis of most statistical inference
errors in collecting data
Errors in Collecting Data
  • sampling error
    • Error caused because no sample is exactly representative of population
    • Chance differences that occur when a sample is selected
  • Non sampling error
    • Error caused by human.
slide15

Population Parameters are computed from a census of the entire Population and are used to describe some characteristic about the Population you are interested in (X).

Population

µx

Parameters

sx

slide16

Population Parameters are computed from a census of the entire Population and are used to describe some characteristic about the Population you are interested in (X).

Population

µx

Parameters

sx

A sample is a subset of a larger Population

sample

sx

sample statistics are computed from sample data and used to estimate Population Parameters

statistics