Quick Summary of Major Changes in the Ninth Edition
Organizational Changes
1. In Chapter 5, Sections 5-3 and 5-4 from the Eighth Edition (nonstandard
normal distributions) are now combined in Section 5-3. This change is
motivated by the new format of Table A-2, which makes it easier for students
to work with normal distributions
2. In Chapter 5, there is a new section discussing "Sampling Distributions
and Estimators," so students can better understand some of the reasons
behind the methods introduced in later chapters. Also, Sections 5-3 and
5-4 from the Eighth Edition have been combined into Section 5-3, which
works with nonstandard normal distributions. Combining of those two sections
is made easier with the new format for Table A-2.
3. In Chapters 6, 7, and, 8, proportions are now covered first, before
means and standard deviations. Reasons for this change: Students see proportions
frequently in the media, and they tend to be more interested in data that
are expressed as proportions. Also, proportions are generally easier to
work with than means, so students can better focus on the important principles
of estimating parameters and testing hypotheses.
4. Section 6-4 from the Eighth Edition (Sample Size Required to Estimate
μ) is now included in Section 6-3 (Estimating a Population Mean: σ Known)
along with confidence intervals for estimating μ.
5. Because the topic of statistical process control is included less frequently
than the topic of nonparametric statistics, those two topics have been
switched so that Chapter 12 now covers methods of nonparametric statistics
and Chapter 13 covers statistical process control.
Content Changes
- Procedures In Chapters 6, 7, 8, there is a change from
"n > 30" to "σ known" as a key criterion
for choosing between the normal and t distributions. This change
reflects the common practice used by working professionals, it provides
more accurate results and it is better for students moving on to other
statistics courses, yet it is not much more difficult than using the
"n > 30" criterion.
- Tables There is a new format for the important normal distribution
in Table A-2: Cumulative areas from the left are now listed on two pages.
Students generally find this format easier to use. Table A-3 has been
expanded to include more of the larger sample sizes for the Student t
distribution.
- Notation In hypothesis testing, the symbols ≥ and ≤ are no
longer used in expressions of the null hypothesis. For claims about a
specific value of a parameter, only the equal symbol = is used. This change
reflects the practice used by the overwhelming majority of professionals
who use methods of statistics and report findings in professional journals.
- Data Sets Appendix B now includes 30 data sets (instead of 20),
including 14 that are new.
- Icons Technology icons [insert icon]are now used to identify exercises
based on larger data sets from Appendix B, which are best completed by
using software or a TI-83 Plus calculator.
- Interpreting Results Throughout the book there is even greater emphasis on interpreting results. Instead of simply obtaining answers, the implications and consequences of answers are considered. For example, when discussing probability in Chapter 3, instead of simply finding probability values, we interpret them by differentiating between events that are usual and those that are unusual. With hypothesis testing, we don't simply end with a conclusion of rejecting or failing to reject a null hypothesis, we proceed to state a practical conclusion that addresses the real issue. Students are encouraged to think about the implications of results instead of cranking out cookbook results that make no real sense.
Exercises
There are over 1500 exercises—more than 58% of them new! In response
to requests by users of the previous edition, there are now more of the
simpler exercises that are based on small data sets. Many more of the
exercises require interpretation of results. Because exercises are of
such critical importance to any statistics book, great care has been taken
to ensure their usefulness, relevance, and accuracy. Three statisticians
have read carefully through the final stages of the book to verify accuracy
of the text material and exercise answers. Exercises are arranged in order
of increasing difficulty by dividing them into two groups: (1) Basic Skills
and Concepts and (2) Beyond the Basics. The Beyond the Basics exercises
address more difficult concepts or require a somewhat stronger mathematical
background. In a few cases, these exercises also introduce a new concept.
Real data: 64% of the exercises use real data. Because the use of real
data is such an important consideration for students, hundreds of hours
have been devoted to finding real, meaningful, and interesting data. In
addition to the real data included throughout the book, many exercises
refer to the 30 data sets listed in Appendix B.
