Chapter 2 Descriptive Statistics - Tabular and Graphical Presentations

# Chapter 2 Descriptive Statistics - Tabular and Graphical Presentations

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Chapter 2 – Descriptive Statistics: Tabular and Graphical Presentations Summarizing Qualitative Data Frequency Distribution - A frequency distribution is a tabular summary of data showering the number (frequency) of items in each of several nonoverlapping classes (Table 2.1, 2.2) - A frequency distribution is created by counting the number of times each item appears Relative Frequency and Percent Frequency Distribution - The relative frequency of a class is the fraction or the proportion of items belonging to a class: Relative Frequency = Frequency of the Class N - The percent frequency of a class is the relative frequency x100 - A relative frequency distribution is a tabular summary of data showing the relative frequency of a class, while a percent frequency distribution summarizes the percent frequency of the data for each class (Table 2.3) Bar Graphs and Pie Charts - A bar graph , or bar chart, is a device that shows qualitative data summarized in a frequency, relative frequency, or percent frequency distribution (Figure 2.1) - Pie charts are another device to express the same qualitative data (Figure 2.2) Summarizing Quantitative Data Frequency Distribution - Three steps are necessary to define the classes for a frequency distribution with quantitative data: 1. Determine the number of nonoverlapping classes a. Specify ranges that will be used to group the data; the smaller the number of data items, the smaller the number of classes 2. Determine the width of each class a. Approximate class width = Largest data value – Smallest data value Number of classes b. Approximate class width can be rounded for convenience 3. Determine the class limits (Table 2.6) a. Limits must be chosen so that each data item belongs to one and only one

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Chapter 2 Descriptive Statistics - Tabular and Graphical Presentations

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