Introduction to Probability and Statistics 14th Edition
What is statistics? Have you ever met a statistician? Do you know what a statistician does? Perhaps you are thinking of the person who sits in the broadcast booth at the Rose Bowl, recording the number of pass completions, yards rushing, or interceptions thrown on New Year’s Day. Or perhaps the mere mention of the word statistics sends a shiver of fear through you. You may think you know nothing about statistics; however, it is almost inevitable that you encounter statistics in one form or another every time you pick up a daily newspaper. Here are some examples concerning the California 2010 elections:
• Rowdy crowd jeers Whitman. GOP candidate criticizes unions; earlier stop draws friendlier audience. GLENDALE— . . . Whitman, a billionaire, has spent $142 million from her personal fortune in the race so far. A Field Poll released Thursday showed her trailing Jerry Brown 49 percent to 39 percent among likely voters.1
• Fiorina calls herself similar to Feinstein, who supports Boxer. MENLO PARK—Republican Carly Fiorina said Friday she would be a like-minded colleague of Democratic Sen. Dianne Feinstein if she unseats Barbara Boxer next week, drawing sharp responses from both Democratic senators. . . . Fiorina, the former CEO of Hewlett-Packard Co., disputed a Field Poll released Friday showing Boxer leading her among likely voters, 49 percent to 41 percent.2
• Race for attorney general tight. Field Poll: Nearly aquarter of those surveyed are undecided. Newsom holds a slim lead over Maldonado for lieutenant governor.
SACRAMENTO—Tuesday’s election for attorney general is a tossup, with Democrat
Kamala Harris and Republican Steve Cooley virtually tied as Harris gains ground in voter-rich
Los Angeles County and among women according to the latest Field Poll.
. . . Today’s poll shows Cooley with 39 percent and Harris with 38 percent among likely
voters. Almost a quarter of likely voters remain undecided.
. . . Newsom, the mayor of San Francisco, leads Maldonado, who was appointed
lieutenant governor this year, 42 percent to 37 percent. A fifth of voters are undecided.
Today’s poll was conducted for The Press-Enterprise and other California media
subscribers. It was conducted October 14 through October 26 and included 1092 voters. It has
a margin of error of plus or minus 3.2 percent.3
—The Press-Enterprise, Riverside, CA
INTRODUCTION TRAIN YOUR BRAIN FOR STATISTICS
Articles similar to these are commonplace in our newspapers and magazines, and in the period just prior to a presidential or congressional election, a new poll is reported almost every day. The language of these articles are very familiar to us; however, they leave the inquisitive reader with some unanswered questions. How were the people in the poll selected? Will these people give the same response tomorrow? Will they give the same response on election day? Will they even vote? Are these people representative of all those who will vote on election day? It is the job of a statistician to ask these questions and to find answers for them in the language of the poll.
Most Believe “Cover-Up” of JFK Assassination Facts
A majority of the public believes the assassination of President John F. Kennedy was part of a larger conspiracy, not the act of one individual. In addition, most Americans think there was a cover-up of facts about the 1963 shooting. Almost 50 years after JFK’s assassination, a FOX news poll shows many Americans disagree with the government’s conclusions about the killing. The Warren Commission found that Lee Harvey Oswald acted alone when he shot Kennedy, but 66 percent of the public today think the assassination was “part of a larger conspiracy” while only 25 percent think it was the “act of one individual.”
“For older Americans, the Kennedy assassination was a traumatic experience that began a loss of confidence in government,” commented Opinion Dynamics President John Gorman.
“Younger people have grown up with movies and documentaries that have pretty much pushed the ‘conspiracy’ line. Therefore, it isn’t surprising there is a fairly solid national consensus that we still don’t know the truth.”
When you see an article like this one in a magazine, do you simply read the title and the first paragraph, or do you read further and try to understand the meaning of the numbers? How did the authors get these numbers? Did they really interview every
American with each political affiliation? It is the job of the statistician to interpret the language of this study.
Hot News: 98.6 Not Normal After believing for more than a century that 98.6 was the normal
For some people at some hours of the day, 99.9 degrees could be fine. And readings as low as 96 turn out to be highly human.
The 98.6 standard was derived by a German doctor in 1868. Some physicians have always been suspicious of the good doctor’s research. His claim: 1 million readings—in an epoch without computers.
So Mackowiak & Co. took temperature readings from 148 healthy people over a three-day period and found that the mean temperature was 98.2 degrees. Only 8 percent of the readings were 98.6.
What questions come to your mind when you read this article? How did the researcher select the 148 people, and how can we be sure that the results based on these 148 people are accurate when applied to the general population? How did the researcher arrive at the normal “high” and “low” temperatures given in the article? How did the German doctor record 1 million temperatures in 1868? Again, we encounter a statistical problem with an application to everyday life.
Statistics is a branch of mathematics that has applications in almost every facet of our daily life. It is a new and unfamiliar language for most people, however, and, like any new language, statistics can seem overwhelming at first glance. But once the language of statistics is learned and understood, it provides a powerful tool for data analysis in many different fields of application.
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