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# ch02 - blu03683_ch02.qxd 04:04 PM Page 33 CHAPTE R How Does...

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2–1 Objectives After completing this chapter, you should be able to 1 Organize data using frequency distributions. 2 Represent data in frequency distributions graphically using histograms, frequency polygons, and ogives. 3 Represent data using Pareto charts, time series graphs, and pie graphs. 4 Draw and interpret a stem and leaf plot. Outline 2–1 Introduction 2–2 Organizing Data 2–3 Histograms, Frequency Polygons, and Ogives 2–4 Other Types of Graphs 2–5 Summary Usage Comparison How Does My Usage Compare? 123 Something Lane Oct 2004 17.2 kWh/day 1.2 therms/day 12.2 kWh/day 0.9 therms/day Oct 2003 10 5 0 15 20 x y Gas use Electric use 2 2 Frequency Distributions and Graphs C H A P T E R (Inset) Copyright 2005 Nexus Energy Software Inc. All Rights Reserved. Used with Permission.

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34 Chapter 2 Frequency Distributions and Graphs 2–2 2–1 Introduction When conducting a statistical study, the researcher must gather data for the particular vari- able under study. For example, if a researcher wishes to study the number of people who were bitten by poisonous snakes in a specific geographic area over the past several years, he or she has to gather the data from various doctors, hospitals, or health departments. To describe situations, draw conclusions, or make inferences about events, the researcher must organize the data in some meaningful way. The most convenient method of organizing data is to construct a frequency distribution. Statistics Today How Serious Are Hospital Infections? According to an article in the Pittsburgh Tribune Review, hospital infections occur in nearly 2 million patients every year. Just how serious a problem is this? It is very serious since the article further reports that one out of every six patients who develop an infec- tion while in the hospital dies. In the first 3 months of 2004, hospitals in Pennsylvania reported that there were 2253 hospital-acquired infections, and 388 deaths resulted from these infections. That is about 17%. The type and number of infections are shown in the following table. Type of infection Infections reported Number of deaths Death rate Urinary tract 931 99 10.6% Surgical site 229 6 2.6 Pneumonia 291 100 34.4 Bloodstream 410 107 26.1 Other 392 76 Varies 2253 388 Looking at the numbers presented in a table does not have the same impact as pre- senting numbers in a well-drawn chart or graph. The article did not include any graphs. This chapter will show you how to construct appropriate graphs to represent data and help you to get your point across to your audience. See Statistics Today—Revisited at the end of the chapter for some suggestions on how to represent the data graphically.
After organizing the data, the researcher must present them so they can be under- stood by those who will benefit from reading the study. The most useful method of pre- senting the data is by constructing statistical charts and graphs. There are many differ- ent types of charts and graphs, and each one has a specific purpose.

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ch02 - blu03683_ch02.qxd 04:04 PM Page 33 CHAPTE R How Does...

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