1 / 22

Social Statistics

Social Statistics. S519: Evaluation of Information Systems. Social Statistics. Statistics describes a set of tools and techniques for describing, organizing and interpreting information or data. Do we need statistics? When and Why?. Why we need statistics.

jasonj
Télécharger la présentation

Social Statistics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Social Statistics S519: Evaluation of Information Systems

  2. Social Statistics • Statistics describes a set of tools and techniques for describing, organizing and interpreting information or data. • Do we need statistics? When and Why?

  3. Why we need statistics • Everybody relies on data in one way or another: • corporate presidents decide company policy based on quarterly sales figures • politicians decide on campaign strategy based on polls • teachers decide grading curves based on a bell curve • you and I decide whether to smoke or not based on health records of other people • Therefore, we need a comprehensive and understandable way to deal with data: • Statistics is the study of making sense of data.

  4. Descriptive statistics • Used to organize and describe the characteristics of a collection of data

  5. Descriptive statistics • How can you describe this table?

  6. Inferential statistics • Make inferences from a smaller group of data to a possible larger one • Sample: a smaller group of data • Population: the whole group of a certain subject

  7. Population & Sample • population • the set of all photographs of Mars • the set of heights of people in the US Army • the set of all measurements of water quality taking from the Hudson river • the set of all problems that can be solved using statistics. • sample • the pictures selected from a specific region of Mars • the heights of people in a particular division of the US Army • the set of water measurements of the Hudson River taken on 7/24/2009 • the statistical problems we are solving in this class

  8. Steps for statistical analysis • Problem definition what is the population of interest, and what are the variables that are to be investigated • Data collection describe and select the sample from the population • Data analysis make some statistical inferences from the sample about the population • Analysis Reporting report the inference together with a measure of reliability for the inference where we use the term variable to mean a characteristic or property of an individual population where the observations can vary.

  9. An example • Example: A tax auditor is responsible for 25,000 accounts. How many accounts are in error? • Defining the problem: The entire population consists of all 25,000 accounts. Our goal is to obtain a reasonable estimate for the number of accounts that are, in all likelihood, in error. Our variable x counts whether an account is in error. • Data collection and summary: The auditor decides to select 2000 accounts at random, tests each of these, and finds that 84 of them are in error. • Data analysis: In this case, the likely theory involves computing 84/2000 = 4.2%. • Analysis reporting: Based on our data analysis we infer that approximately 4.2% of the accounts will be in error.

  10. Tools • Excel • Excel Toolpak • SPSS/PASW

  11. Excel Toolpak (1) • Click the Microsoft Office Button , and then click Excel Options. • Click Add-Ins, and then in the Manage box, select Excel Add-ins. • Click Go. • In the Add-Ins available box, select the Analysis ToolPak check box, and then click OK. • If you get prompted that the Analysis ToolPak is not currently installed on your computer, click Yes to install it. • After you load the Analysis ToolPak, the Data Analysis command is available in the Analysis group on the Data tab.

  12. Excel Toolpak (2) • Powerful, reliable, accessible, easy, and free

  13. Formula How does it work in Excel?

  14. Basics of a Spreadsheet • So let's get started digging into what makes a spreadsheet work. Spreadsheets are made up of: • columns • Rows • cells • In each cell there may be the following types of data: • text (labels) • number data (constants) • formulas (mathematical equations)

  15. Column

  16. Row

  17. Cell

  18. Types of Data ALL formulas MUST begin with an equal sign (=).

  19. Formulas – SUM • The Sum function takes all of the values in each of the specified cells and totals their values. The syntax is: =SUM(first value, second value, etc)

  20. Formulas – AVERAGE • The average function finds the average of the specified data. The syntax is as follows =Average(first value, second value, etc.)

  21. Formulas – MAX/MIN • MAX: This will return the largest (max) value in the selected range of cells. • MIN: This will return the smallest (Min) value in the selected range of cells.

  22. Formulas – COUNT • This will return the number of entries (actually counts each cell that contains number data) in the selected range of cells.

More Related