Chapter 2 Describing Data http statisticdescriptive wordpress com

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

Constructing A Frequency Table o 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. 2

Table 2 -1 Frequency Table For Vehicles Sold At Whitner Autoplex Last Month Car Type Number Of Car Domestic 50 Foreign 30 Chapter 2. Describing Data Ir. Muhril Ardiansyah, M. Sc. , Ph. D. 3

Constructing A Frequency Table (continued) o 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. 4

Table 2 -2 Relative Frequency Table Of Vehicles Sold Vehicle Type Number Sold Relative Frequency Domestic 50 50/80 =0. 625 Foreign 30 30/80=0. 3 75 Total 80 80/80=1 Chapter 2. Describing Data Ir. Muhril Ardiansyah, M. Sc. , Ph. D. 5

Constructing A Frequency Table (continued) o 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. 6

Constructing A Frequency Table (continued) o 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. 7

Constructing Frequency Distributions: Quantitative Data o 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. 8

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. 9

The Steps For Organizing Data Into A Frequency Distribution o o o 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. 10

Step 1: Decide on the number of classes n = 80 If k = 6 (k is number of classes) Then: 2 k 26 = 64, still less than 80 not using k =6 If k = 7 Then: 2 k 27 = 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. 11

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 Chapter 2. Describing Data Ir. Muhril Ardiansyah, M. Sc. , Ph. D. 12

Step 3: Set the individual class limits 15000 18000 21000 24000 27000 30000 33000 up up Chapter 2. Describing Data to to 18000 21000 24000 27000 30000 33000 36000 Ir. Muhril Ardiansyah, M. Sc. , Ph. D. 13

Step 4: Tally the vehicle selling prices into the classes Class 15000 18000 21000 24000 27000 30000 33000 up up to to Chapter 2. Describing Data 18000 21000 24000 27000 30000 33000 36000 Tallies IIIII IIIII IIIII III IIIII II Ir. Muhril Ardiansyah, M. Sc. , Ph. D. 14

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

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

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

Selling Price 15000 up to 18000 up to 21000 up to 24000 up to 27000 up to 30000 up to 33000 up to TOTAL Chapter 2. Describing Data 18000 21000 24000 27000 30000 33000 36000 Frequency 8 23 17 18 8 4 2 80 Ir. Muhril Ardiansyah, M. Sc. , Ph. D. Relative Freq 0. 1 0. 2875 0. 2125 0. 2250 0. 1 0. 05 0. 025 1. 00 18

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

o 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. 20

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

http: //statisticdescriptive. wordpress. com/ Chapter 2. Describing Data Ir. Muhril Ardiansyah, M. Sc. , Ph. D. 22

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. Chapter 2. Describing Data Ir. Muhril Ardiansyah, M. Sc. , Ph. D. 23