0.1 Descriptive Statistics (Chapters 1-2)

Transcription

1 Chapter 0 What is Statistics Statistics is concerned with the development and application of processes, methods, and techniques for collecting, analyzing, and interpreting data to aid in decision making. We can be roughly divided the course into 3 parts: 0.1 Descriptive Statistics (Chapters 1-2) Consists of a set of procedures that is used to organize, summarize and present numericaldatainaninformativeway. This may involve a tabulation or graph of the general characteristics of a set of data Presentation of some specific characteristics such as measures of central tendency (means) or measures of dispersion (variances). 0.2 Probability (Chapters 3-5) The concept of probability arises when we consider taking a sample from a population andthenwishtomakestatementsaboutthelikelihoodofthesamplehaving a certain characteristics. Population or Universe is a set or a collection of items of all possible observations of items of some specific characteristic. Sample is a subset of items from the population. 1

2 2 CHAPTER 0. WHAT IS STATISTICS Key Definitions A population is the collection of all items of interest or under investigation N represents the population size A sample is an observed subset of the population n represents the sample size A parameter is a specific characteristic of a population A statistic is a specific characteristic of a sample Statistics for Business and Economics, 6e 2007 Pearson Education, Inc. Chap 1-5 Figure 1:

3 0.3. SAMPLING AND INFERENTIAL STATISTICS (CHAPTERS 6-10) Example of Probability Question The manager of a hospital laboratory knows that 5% ofthelab stestshavetobererun. Her subordinates perform 10 tests in one morning. Question: Whatisthechanceshewillhavetorerunnoneofthemagain. Population = Good/Bad Tests Sample = 10 tests What will sample look like? 0.3 Sampling and Inferential Statistics (Chapters 6-10) Consists of a set of procedures that enable a statistician to make statements (inferences or predictions) about the population from information contained in the observed sample 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 Inference is the process of drawing conclusions or making decisions about a population based on sample results Statistics for Business and Economics, 6e 2007 Pearson Education, Inc. Chap 1-11 Figure 2:

4 4 CHAPTER 0. WHAT IS STATISTICS 0.4 Types and Sources of Data Types of Data Data Categorical Numerical Examples: Marital Status Are you register ed to vote? Eye Color (Defi ned categories or groups) Discrete Examples: Number of Children Defects per hour (Counted items) Continuous Examples: Weight Voltage (Measured characteristics) Statistics for Business and Economics, 6e 2007 Pearson Education, Inc. Chap 2-3 Figure 3:

5 0.5. SOURCES OF DATA 5 Quantitative Data (Continuous Variables) are data that are measured on a scale. Examples are prices, incomes, etc. Qualitative or Categorical data (Discrete Data) are observations that can be classified into a single category or a set of categories. Example are sex, marital status, employment status. Cross-section data: Data measured at a point in time. Sales of computers at IBM on June 10,1966. Time Series Data: Data measured over time. Quarterly GNP form 1970 Q Q4 Two kinds of studies: 1. Observational Studies: The investigator collects or observes (historical) data of interest that is not under control of the investigator. 2. Experimental Studies:The investigator directly controls or designs the experiment (as in a laboratory set-up) to collect the data of interests. Collecting data via question surveys may be thought of as experimental since the researcher designs the questions which will influence the responses. 0.5 Sources of Data Library contains written government documents, international statistics gathered by such organizations as the OECD, IMF United Nations, etc. Computer databanks that contain large amounts of information that may be readily accessed by the researcher. In Canada, the main data source is the CANSIM databank which is available on the Queen s Economic Homepage (see Resources for Economists). Others databases include CRSP, CITIBASE and IFS datatape. 0.6 Statistical Graphics Perhaps the biggest influence of the personal computer in statistics is the advances made in graphical presentation of information.

6 6 CHAPTER 0. WHAT IS STATISTICS Graphical Presentation of Data Techniques reviewed in this chapter: (continued) Categorical Variables Frequency distribution Bar chart Pie chart Pareto diagram Numerical Variables Line chart Frequency distribution Histogram and ogive Stem-and-leaf display Scatter plot Statistics for Business and Economics, 6e 2007 Pearson Education, Inc. Chap 2-6 Figure 4: Check the remaining examples in Chapter 1 for other graphs and charts

7 0.6. STATISTICAL GRAPHICS 7 Bar Chart Example Hospital Unit Number of Patients Cardiac Care 1,052 Emergency 2,245 Intensive Care 340 Maternity 552 Surgery 4,630 Number of patients per year Hospital Patients by Unit Cardiac Care Emergency Intensive Care Maternity Su rgery Statistics for Business and Economics, 6e 2007 Pearson Education, Inc. Chap 2-10 Figure 5: Pie Chart Example Hospital Number % of Unit of Patients Total Cardiac Care 1, Emergency 2, Intensive Care Maternity Surgery 4, Hospital Patients by Unit Cardiac Care 12% Sur gery 53% Emergency 25% (Percentages are rounded to the nearest percent) Intensive Care 4% Maternity 6% Statistics for Business and Economics, 6e 2007 Pearson Education, Inc. Chap 2-11 Figure 6:

8 8 CHAPTER 0. WHAT IS STATISTICS Line Chart Example Magazine Subscriptions by Year Thousands of subscribers Statistics for Business and Economics, 6e 2007 Pearson Education, Inc. Chap 2-17 Figure 7: