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Chapter 3

# Changping Wang - QMS 102 Chapter 3.docx

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Quantitative Methods

QMS 102

Scott Clark

Winter

Description

QMS: Chapter 3
3.1 How Do You Organize Quantitative Data Graphically?
• Present ration and interval data using histograms, polygons, Ogives, stem-and-
leaf plots, frequency distribution, contingency table and scatter plot
3.2 Stem-and-Leaf Plot
• Looks like a horizontal bar chart maintaining most of the original data values
• Ex: Value of 84 can be represented into “8” (stem value) and “4” (leaf value)
• Example of a stem-and-leaf plot:
Hospitality Industries: Profits ($)
Stem (100,00) Leaf (10,000)
1 1234
1 55688
2 2
2 56
3 113
3 79
• You must have a title for a stem-and-leaf plot. The bracket values tell us how
much each stem or leaf is worth (Stems: 100,000; 200,000; 300,000; etc.)
• Entry one is 1 and its value is 100,000 so we do 1*100,000 because going up by
100,000s is too big, breaks rules
• Stem: 1*100,000; Leaf: 1*10,000; add them up = 110,000 for first value, & so on
3.3 Rules and Convention to Construct a Stem-and-Leaf Plot
• Stem Rules:
1. Number of stems should be from 6-13
2. Stem values should be consecutive numbers or repeated numbers (twice or five
times)
3. Stem units must be indicated if the stem is not to be taken at face value
4. There must be at least one leaf associated with the first and last stem
• Leaf Rules:
1. Leaf for each data value is the next single digit after the stem. If stem is repeated
twice: values 0-4 go on first stem and 5-9 on second stem. If its repeated 5 times:
0-1 on stem 1, 2-3 on stem 2, 3-4 on stem 3, etc. Reversed if stems are negative
2. No rounding off
3. Leaf values are in ascending order (positive) & descending order (negative)
4. Leaf values must be evenly spaced
5. No commas or dashes between the numbers are allowed
3.4 How Do You Construct a Stem-and-Leaf Plot Using Data with Positive Values?
1. Sort the data in ascending order; you can use the calculator to make it faster
2. Find the maximum and minimum values
3. Split the minimum and maximum values i

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