Chapter Two

Chapter Two - Lecture Notes Chapter Two: Methods for...

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Lecture Notes Chapter Two: Methods for Describing Sets of Data Randall Miller 1 | Page 1. Describing Qualitative Data Definition 2.1 A class is one of the categories into which qualitative data can be classified. Definition 2.2 The class frequency is the number of observations in the data set that fall into a particular class. Definition 2.3 The class relative frequency is the class frequency divided by the total number of observations in the data set; that is, class frequency class relative frequency n = Definition 2.4 The class percentage is the class relative frequency multiplied by 100; that is, ( ) class percentage class relative frequency *100 = Summary of Graphical Descriptive Methods for Qualitative Data Bar Graph : The categories (classes) of the qualitative variable are represented by bars, where the height of each bar is either the class frequency, class relative frequency, or class percentage. Pie Chart : The categories (classes) of the qualitative variable are represented by slices of a pie (circle). The size of each slice is proportional to the class relative frequency. Pareto Diagram : A bar graph with the categories (classes) of the qualitative variable (i.e., the bars) arranged by height in descending order from left to right. 2. Graphical Methods for Describing Quantitative Data Determining the Number of Classes in a Histogram Number of Observations in Data Set Number of Classes Fewer than 25 5 – 6 25 - 50 7 – 14 More than 50 15 - 20 Summary of Graphical Descriptive Methods for Quantitative Data Dot Plot : The numerical value of each quantitative measurement in the data set is represented by a dot on a horizontal scale. Then data values repeat, the dots are placed above one another vertically.
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Lecture Notes Chapter Two: Methods for Describing Sets of Data Randall Miller 2 | Page Stem-and-Leaf Diagram : The numerical value of the quantitative variable is partitioned into a “stem” and a “leaf.” The possible stems are listed in order in a column. The leaf for each quantitative measurement in the data set is placed in the corresponding stem row.
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This note was uploaded on 07/23/2011 for the course STA 3123 taught by Professor Staff during the Fall '08 term at FIU.

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Chapter Two - Lecture Notes Chapter Two: Methods for...

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