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Variables

Variables. 9/17/2013. Exam 1 9/19. Exam 1 9/19 It is an in class exam. You do not need an exam book You can use a basic calculator. Opportunities to discuss course content. Office Hours For the Week. When Wednesday 8- 9:15, 10:15-12 Thursday 8-12 And by appointment.

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Variables

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  1. Variables 9/17/2013

  2. Exam 1 9/19 • Exam 1 9/19 • It is an in class exam. You do not need an exam book • You can use a basic calculator

  3. Opportunities to discuss course content

  4. Office Hours For the Week • When • Wednesday 8- 9:15, 10:15-12 • Thursday 8-12 • And by appointment

  5. Course Learning Objectives • Students will learn the basics of research design and be able to critically analyze the advantages and disadvantages of different types of design.  • Students Will be able to interpret and explain empirical data.

  6. Descriptive statistics

  7. Descriptive Statistics • These simply describe the attributes of a single variable. • You cannot test here (you need two variables) • Why do them?

  8. Categories of Descriptive Statistics Measures of Central Tendency Measures of Dispersion How wide is our range of data, how close to the middle are the values distributed Range, Variance, Standard Deviation • The most common, the middle, the average • Mean, Median and Mode

  9. The Mode • the most frequent observation of the variable in a distribution • Which category is most common • There can be more than 1

  10. Examples • What are the Modes here? • 110,105.100.100.100.100.99.98 • 110.105.105.105.100.95.95.95.90

  11. The 2006 Election in Texas Values Ignore Missing/System Categories

  12. Advantages and Disadvantages • Advantages of the Mode • Disadvantages of the Mode

  13. Where Parties Should Go in A Normal Distribution They Move To the Center, why?

  14. What About A Bimodal Distribution?

  15. Party Polarization

  16. A polymodal System

  17. The Median

  18. The Median • It only tells us one thing • 50% above, 50% below • the value that lies in the middle of the data when arranged in ascending order.

  19. Examples • The University of Texas • The 78704 Zip Code

  20. About the Median • Characteristics and problems of the median • The middle observation = (N+1)/2 • Three Examples • (105,102,101,92,91,80) • (133,113,112,95,94) • (27,12,78,104,45,34)

  21. Locating the Median

  22. You can also look here for where 50% falls Finding the Median Ignore Missing Values • location of median case (1747+1)/2 = 874 • Where Does that case fall? • Case 1 through 534 = has value of 0 • Case 535 through 1747 = has value of 1 • Case 874 is more than 535 and less than 1747 • THE MEDIAN IS 1, the category is voted

  23. Lets Try Again Values Only Use Valid Cases

  24. The Answer location of median case (1454+1)/2 = 727.5 Where Does that case fall? Cases 1 through 74 = has value of 1 Cases 75 through 502= has value of 2 Cases 503 through 1454= as a value of 3 Case 727.5 is more than 503 THE MEDIAN IS 3, the category is not at all scientific The 50% falls in here

  25. Median Voter Theory

  26. The Mean

  27. The Mean • What is it • How do you compute it?

  28. About the Mean • Characteristics of the Mean • Problems of the Mean

  29. An Example

  30. Picking the Right Measure

  31. Frequency Distributions

  32. To Run A Frequency Distribution • Open GSS2008.sav • Analyze (95% of all our statistics will come from here) • Descriptive Statistics • Frequencies

  33. Step 2 Select Your Variable Here is the Output

  34. Interpreting the Results What is the Mode (#, cat)? • Percent- relative frequency for all cases • Valid Percent- relative frequency for valid cases (This excludes missing values). • Cumulative Percent- %of observations less than or equal to the category What is the median (#, cat?)

  35. Measures of Central Tendency

  36. First Run A Frequency Distribution Natenvir Variable- Government Spending on Improving and Protecting The Environment The Statistics Window Click on Statistics

  37. The Output

  38. For Ratio Variables Step 2 Step 4 Step 1 Step 3

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