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Chapter 2. Describing Data

Chapter 2. Describing Data. http://statisticdescriptive.wordpress.com/. Constructing A Frequency Table. Frequency table: a grouping of qualitative data into mutually exclusive classes showing the number of observation in each class. Class frequency:

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Chapter 2. Describing Data

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  1. Chapter 2.Describing Data http://statisticdescriptive.wordpress.com/ Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  2. Constructing A Frequency Table • Frequency table: a grouping of qualitative data into mutually exclusive classes showing the number of observation in each class. Class frequency: the number observations in each class Table 2-1 Page 22 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  3. Table 2-1 Frequency Table For Vehicles Sold At Whitner Autoplex Last Month Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  4. Constructing A Frequency Table (continued) • Relative class frequencies: show the fraction of the total number of observation in each class. Table 2-2 Page 23 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  5. Table 2-2 Relative Frequency Table Of Vehicles Sold Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  6. Constructing A Frequency Table (continued) • Graphic presentation of qualitative data: - bar chart a graph in which the classes are reported on the horizontal axis, and the class frequencies on the vertical axis. Chart 2-1 Page 23 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  7. Constructing A Frequency Table (continued) • Graphic presentation of qualitative data: - Pie chart a chart that shows the proportion or percent that each class represents of the total number of frequencies. Chart 2-2 Page 24 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  8. Constructing Frequency Distributions: Quantitative Data • Frequency distribution: a grouping of data into mutually exclusive classes showing the number of observations in each class. Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  9. Table 2-4 Page 28Prices of vehicles sold last month at Whitner Autoplex $23197 $23372 $20454 $26651 ……………………………………………………………… …………………………………………………………….. n = 80 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  10. The Steps For Organizing Data Into A Frequency Distribution • Step 1: Decide on the number of classes. • Step 2: Determine the class interval or width. • Step 3: Set the individual class limits. • Step 4: Tally the vehicle selling prices into the classes. • Step 5: Count the number of items in each class. Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  11. Step 1: Decide on the number of classes n = 80 If k = 6 (k is number of classes) Then: 2k 26 = 64, still less than 80 not using k =6 If k = 7 Then: 2k 27 = 128, greater than 80 Decide at least k = 7 Can choose k more than 7 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  12. Step 2: Determine the class interval or width i more or equal (H – L)/ k i = class interval H = the highest observed value L = the lowest observed value H = 35925 L = 15546 i = (35925-15546)/7 = 2911 = 3000 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  13. Step 3: Set the individual class limits 15000 up to 18000 18000 up to 21000 21000 up to 24000 24000 up to 27000 27000 up to 30000 30000 up to 33000 33000 up to 36000 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  14. Step 4: Tally the vehicle selling prices into the classes Class Tallies 15000 up to 18000 IIIII III 18000 up to 21000 IIIII IIIII IIIII IIIII III 21000 up to 24000 IIIII IIIII IIIII II 24000 up to 27000 IIIII IIIII IIIII III 27000 up to 30000 IIIII III 30000 up to 33000 IIII 33000 up to 36000 II Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  15. Step 5: Count the number of items in each class Selling Price Frequency 15000 up to 18000 8 18000 up to 21000 23 21000 up to 24000 17 24000 up to 27000 18 27000 up to 30000 8 30000 up to 33000 4 33000 up to 36000 2 TOTAL 80 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  16. Class Intervals And Class Midpoints Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  17. Relative Frequency Distribution • A relative frequency distribution: converts the frequency to a percent. Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  18. Selling Price Frequency Relative Freq 15000 up to 18000 8 0.1 18000 up to 21000 23 0.2875 21000 up to 24000 17 0.2125 24000 up to 27000 18 0.2250 27000 up to 30000 8 0.1 30000 up to 33000 4 0.05 33000 up to 36000 2 0.025 TOTAL 80 1.00 Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  19. Graphic Presentation Of A Frequency Distribution: • Histogram. • Frequency polygon. Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  20. Histogram: a graph in which the classes are marked on the horizontal axis and the class frequencies on the vertical axis. The class frequencies are represented by the heights of the bars and the bars are drawn adjacent to each other. Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  21. Frequency polygon: the class midpoints are connected with a line segment. Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  22. http://statisticdescriptive.wordpress.com/ Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

  23. Quiz The following is the number of minutes to commute from home to work for a group of automobile executives; 28 25 48 37 41 19 32 26 16 23 23 29 36 31 26 21 32 25 31 43 35 42 38 33 28 Make frequency distribution included relative freq. Ir.Muhril Ardiansyah,M.Sc.,Ph.D.

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