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School
Ryerson University
Department
Quantitative Methods
Course
QMS 102
Professor
Sheila Rosenberg
Semester
Fall

Description
Alyssa Soubliere September 16, 2013 Ryerson University QMS102 Lecture Two Notes LectureTwo Notes Graphical Presentation of Qualitative Data  We cannot perform calculations of qualitative (nominal or ordinal) data, but…  You can perform calculations on the number of responses in each category  To graphically present qualitative data we use: o Bar charts (horizontal or vertical) o Pie Charts o Pareto Charts (look like bar charts, but with an additional piece of information)  See example 2.2, 2.3 & 2.4 on pg. 40-43 from textbook  In a bar chart, a bar shows each category, the length represents the amount, frequency or percentage of values falling into a category which come from the summary table of the variable  A pie chart is a circle broken into segments that represent categories. The size of each slice of the pie varies according to the percentage in each category  Named after the 19 century Italian economist Vilfredo Pareto whose research discovered that 80% of the wealth is owned by 20% of the population o Generalized as the 80/20 rule o Is a combination of a vertical bar chart, where categories are shown in descending order of frequency and a cumulative polygon shown in the same graph o Is used to separate the vital few from the trivial many o A Pareto chart, besides the frequency/percentage one also needs a cumulative percentage (has to add up to 100) Graphical Presentation of Quantitative Data  A Stem-and-Leaf Plot is an easy way to o Summarize the distribution (or shape) of quantitative data o See where the concentration of quantitative data exist o Retain most of the data values (numbers) o Is used if the data has no more than 50 values  We start by separating the sorted data series into leading digits (the stems) and the trailing digits (the leaves)  The decimal system is the most common base for representation of numbers  We use numbers 0,1,2,3,4,5,6,7,8,9 to represent integers, fractions, and real numbers  9765= 9*10^3 + 7*10^2 + 6*10^1 + 5  9,765= 9 + 7 * 10^-1 + 6 * 10 ^-2 + 5 * 10^-3  If we have a data value 84 we can take a stem (in units of 10) to be 8 and a leaf to be 4 since 84 = 8 * 10 + 4  If we have a data value 13000 we can take a stem (in units of 10000) to be 1 and a leaf to be 3 since 13000 = 1*10^4 + 3*10^3 Alyssa Soubliere September 16, 2013 Ryerson University QMS102 Lecture Two Notes Stem-and-Leaf Plot Rules:  The Stem Rules: 1. The number of stems should be from 6 to 13 2. Stem values should
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