Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.1 Chapter 2. Describing Data

Chapter 2. Describing Data 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

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.3 Table 2-1 Frequency Table For Vehicles Sold At Whitner Autoplex Last Month Car TypeNumber Of Car Domestic50 Foreign30

Chapter 2. Describing Data 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

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.5 Table 2-2 Relative Frequency Table Of Vehicles Sold Vehicle TypeNumber SoldRelative Frequency Domestic5050/80 =0.625 Foreign3030/80=0.375 Total8080/80=1

Chapter 2. Describing Data 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

Chapter 2. Describing Data 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

Chapter 2. Describing Data 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.

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

Chapter 2. Describing Data 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.

Chapter 2. Describing Data 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: 2 k 2 6 = 64, still less than 80 not using k =6 If k = 7 Then: 2 k 2 7 = 128, greater than 80 Decide at least k = 7 Can choose k more than 7

Chapter 2. Describing Data 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 = L = i = ( )/7 = 2911 = 3000

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.13 Step 3: Set the individual class limits up to up to up to up to up to up to up to 36000

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.14 Step 4: Tally the vehicle selling prices into the classes Class Tallies up to IIIII III up to IIIII IIIII IIIII IIIII III up to IIIII IIIII IIIII II up to IIIII IIIII IIIII III up to IIIII III up to IIII up to II

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.15 Step 5: Count the number of items in each class Selling Price Frequency up to up to up to up to up to up to up to TOTAL 80

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.16 Class Intervals And Class Midpoints

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.17 Relative Frequency Distribution  A relative frequency distribution: converts the frequency to a percent.

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.18 Selling Price Frequency Relative Freq up to up to up to up to up to up to up to TOTAL

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.19 Graphic Presentation Of A Frequency Distribution: 1.Histogram. 2.Frequency polygon.

Chapter 2. Describing Data 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.

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.21  Frequency polygon: the class midpoints are connected with a line segment.

Chapter 2. Describing Data Ir.Muhril Ardiansyah,M.Sc.,Ph.D.22

Chapter 2. Describing Data 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; Make frequency distribution included relative freq.