Chapt2

# Chapt2 - 1 Chapter 2 Methods for Describing Sets of Data...

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Unformatted text preview: 1 Chapter 2 Methods for Describing Sets of Data Objective 1: Know Qualitative compared to Quantitative information 1. Qualitative—categorical information Examples: 1. Quantitative— true numerical information Examples: 2 Describing Sets of Data After the data or information has been collected, the first step in research is to summarize the information. Objective 2: Understand approaches to summarizing information Different approaches are required for qual. Vs. quant. Information. Section 2.1 Qualitative Section 2.2 Quantitative 3 2.1 Describing Qualitative Data Information that is categorical (not numeric) can be summarized by: • graphical methods (pie chart and bar charts) • a frequency table displaying all groups • by listing information such as the largest (freq or percent) category • Specific important findings • Cannot calculate a mean or median • Cannot calculate a numeric measure of variability 4 2.1 Definitions Class— one of the categories into which data can be classified Class Frequency— number of observations (data values or measurements) in a particular class Class relative frequency— class frequency divided by the total number of observations in the data set 5 Example: What month were you born? Start collecting information: Jan, Mar, Mar, Apr, Dec, Aug, Aug, Oct, Oct, Oct, Feb, etc… Continue asking every person in your sample. What are the classes for this problem? How would we find the class frequency? 6 Frequency Table: Class Frequency Relative Frequency Winter (Dec, Jan and Feb) 16 16/50 = . 32 Spring (Mar, Apr and May) 12 .24 Summer (Jun, Jul, and Aug) 8 .16 7 Bar Chart Season of Birth 2 4 6 8 10 12 14 16 18 Winter Spring Summer Fall Season Number of people Series1 8 Pie Chart Winter 32% Spring 24% Summer 16% Fall 28% 9 2.2 Graphical Methods for Describing Quantitative Data The appropriate way to summarize Quantitative information is to use some graphical approach ( histogram, stem and leaf or box plot ) and numerical summary information ( mean and variance ) 10 2.2 Graphical Methods for Describing Quantitative Data Stem-and-Leaf Displays--represents each observation by its leading digit (the stem) and by its final digit (the leaf) EX. Number of phone numbers 41 56 62 68 70 72 76 76 76 76 78 80 84 86 88 92 92 94 96 96 11 Ex. Continued Stem(tens) Leaf(ones) 4 5 6 7 8 9 2 1 6 8 12 Ex. Continued Stem(tens) Leaf(ones) 4 5 6 7 8 9 2 8 1 6 0 2 6 6 6 6 8 0 4 6 8 2 2 4 6 6 13...
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Chapt2 - 1 Chapter 2 Methods for Describing Sets of Data...

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