I GENERAL COMMENTS
COURSE DESIGN
To provide flexibility in course design, a number of sections in the textbook are designated
as "Optional." The instructor wishing to adopt a leisurely pace, or who is designing a course
for one quarter, can omit all optional sections and, moreover, give only light coverage to
some other sections. The Comments on Chapters in Section II of this Manual indicate
specifically those sections and parts of sections where light coverage may be appropriate.
For an even briefer schedule, Chapters 11 and 12 can be omitted entirely. Also, there is no
new material in Chapter 13; rather, this chapter provides a perspective of the preceding
chapters. The purpose of Chapter 13 is to help summarize and put into perspective the
many inference methods discussed in the text.
Because each chapter builds on the preceding ones, it is not advisable to alter the order of
the chapters. However, it would be possible to postpone coverage of Section 6.6 (on
confidence intervals for proportions) until covering hypothesis testing for categorical data
in Chapter 10. (This was the placement of confidence intervals for proportions in the first
edition; the third edition treats confidence intervals for means and for proportions together
in Chapter 6.)
EXERCISES
Calculators and Computers
The exercises in the text are designed to minimize numerical drudgery and emphasize
understanding. Exercises with simple numbers familiarize the students with the meaning
and structure of formulas, after which additional exercises, based on real data, focus
primarily on interpretation. Any calculations required for the latter exercises are easily
carried out on a hand calculator.
,If computing facilities are available, the use of a computer can be easily integrated into the
course. To that end, a data disk comes with the textbook. A number of the exercises give
raw data and could be done on either a computer or a calculator. Also, certain exercises,
labeled computer exercise, are especially designed for computer use and would not be
suitable for hand computation.
Location of Exercises
Most exercises are located at the ends of sections. At the end of each chapter are
Supplementary Exercises, some of which use material from more than one section.
Class Discussion
Many of the exercises can be used as starting points for class discussion. This is especially
true of exercises that emphasize interpretation of results or that request a critique of an
inappropriate analysis or conclusion.
,Sampling Exercises
Scattered throughout the first half of the book are exercises that require students to carry
out random sampling. These sampling exercises are discussed in detail in Section III of this
Manual.
APPENDICES
At the end of the textbook are appendices that provide more detail on selected topics
discussed in the text. These appendices are not intended to form part of the course (except,
perhaps, for Appendix 6.1 on significant digits), but rather to provide supplementary
material for interested students.
STATISTICAL TABLES
The tables of critical values are all used in essentially the same way. In the t table (Table 4
and inside back cover), the column headings are upper tail areas. Thus, when the
alternative hypothesis for a t test is directional, students can easily bracket the P-value by
reading the column headings; when the alternative hypothesis is nondirectional, the column
headings must be multiplied by 2. The tables for the Wilcoxon-Mann-Whitney test, the sign
test, and the Wilcoxon signed-rank test give two sets of column headings: one for use with
nondirectional alternatives and one for use with directional alternatives. Tables for the chi-
square test and the F test give upper tail areas, as is appropriate for use with the usual
nondirectional alternative hypotheses. When the alternative hypothesis in a chi-square test
is directional, the column headings must be multiplied by 1/2.
The examples in the textbook and the answers to the exercises in this Manual do not use
interpolation in the statistical tables. For instance, in entering Table 4 the nearest value of
df is used; in ambiguous cases (e.g., df = 35 or df = 200), either one of the nearest values is
considered correct. Students may need some guidance on this point.
, IICOMMENTS ON CHAPTERS
Chapter 1 Introduction
The study of statistics will seem more inviting to students in the life sciences if they see
that statistical questions arise in biologically interesting settings. Chapter 1 consists
primarily of a series of examples of such settings. Instructors may choose to discuss
these or other examples in the first lecture.
Chapter 2 Description of Samples and Populations
Comments on Sections 2.1 - 2.3
Students are sometimes uneasy when approaching these introductory sections because
they are not sure what is expected of them. The instructor may wish to reassure them on
the following points: (a) the distinction between Y and y in Section 2.1 is for clarity only;
(b) for an exercise requiring a grouped frequency distribution, there are many different
"right answers"; (c) the material on histograms with unequal class widths is for
"consciousness-raising" purposes -- the exercises do not require students to create such
histograms.
Comments on Sections 2.4 - 2.6
This is an opportunity to get students started using their calculators effectively. Two
useful general principles are:
(a) Minimize roundoff error by keeping intermediate answers in the calculator rather
than writing them down. Round the answers only at the end of the entire
computation. (The topic of how far to round when reporting the mean and SD is
discussed in Section 6.2; for use in Chapter 2, the instructor may wish to give students
a temporary answer, such as "always round to four significant digits.")
COURSE DESIGN
To provide flexibility in course design, a number of sections in the textbook are designated
as "Optional." The instructor wishing to adopt a leisurely pace, or who is designing a course
for one quarter, can omit all optional sections and, moreover, give only light coverage to
some other sections. The Comments on Chapters in Section II of this Manual indicate
specifically those sections and parts of sections where light coverage may be appropriate.
For an even briefer schedule, Chapters 11 and 12 can be omitted entirely. Also, there is no
new material in Chapter 13; rather, this chapter provides a perspective of the preceding
chapters. The purpose of Chapter 13 is to help summarize and put into perspective the
many inference methods discussed in the text.
Because each chapter builds on the preceding ones, it is not advisable to alter the order of
the chapters. However, it would be possible to postpone coverage of Section 6.6 (on
confidence intervals for proportions) until covering hypothesis testing for categorical data
in Chapter 10. (This was the placement of confidence intervals for proportions in the first
edition; the third edition treats confidence intervals for means and for proportions together
in Chapter 6.)
EXERCISES
Calculators and Computers
The exercises in the text are designed to minimize numerical drudgery and emphasize
understanding. Exercises with simple numbers familiarize the students with the meaning
and structure of formulas, after which additional exercises, based on real data, focus
primarily on interpretation. Any calculations required for the latter exercises are easily
carried out on a hand calculator.
,If computing facilities are available, the use of a computer can be easily integrated into the
course. To that end, a data disk comes with the textbook. A number of the exercises give
raw data and could be done on either a computer or a calculator. Also, certain exercises,
labeled computer exercise, are especially designed for computer use and would not be
suitable for hand computation.
Location of Exercises
Most exercises are located at the ends of sections. At the end of each chapter are
Supplementary Exercises, some of which use material from more than one section.
Class Discussion
Many of the exercises can be used as starting points for class discussion. This is especially
true of exercises that emphasize interpretation of results or that request a critique of an
inappropriate analysis or conclusion.
,Sampling Exercises
Scattered throughout the first half of the book are exercises that require students to carry
out random sampling. These sampling exercises are discussed in detail in Section III of this
Manual.
APPENDICES
At the end of the textbook are appendices that provide more detail on selected topics
discussed in the text. These appendices are not intended to form part of the course (except,
perhaps, for Appendix 6.1 on significant digits), but rather to provide supplementary
material for interested students.
STATISTICAL TABLES
The tables of critical values are all used in essentially the same way. In the t table (Table 4
and inside back cover), the column headings are upper tail areas. Thus, when the
alternative hypothesis for a t test is directional, students can easily bracket the P-value by
reading the column headings; when the alternative hypothesis is nondirectional, the column
headings must be multiplied by 2. The tables for the Wilcoxon-Mann-Whitney test, the sign
test, and the Wilcoxon signed-rank test give two sets of column headings: one for use with
nondirectional alternatives and one for use with directional alternatives. Tables for the chi-
square test and the F test give upper tail areas, as is appropriate for use with the usual
nondirectional alternative hypotheses. When the alternative hypothesis in a chi-square test
is directional, the column headings must be multiplied by 1/2.
The examples in the textbook and the answers to the exercises in this Manual do not use
interpolation in the statistical tables. For instance, in entering Table 4 the nearest value of
df is used; in ambiguous cases (e.g., df = 35 or df = 200), either one of the nearest values is
considered correct. Students may need some guidance on this point.
, IICOMMENTS ON CHAPTERS
Chapter 1 Introduction
The study of statistics will seem more inviting to students in the life sciences if they see
that statistical questions arise in biologically interesting settings. Chapter 1 consists
primarily of a series of examples of such settings. Instructors may choose to discuss
these or other examples in the first lecture.
Chapter 2 Description of Samples and Populations
Comments on Sections 2.1 - 2.3
Students are sometimes uneasy when approaching these introductory sections because
they are not sure what is expected of them. The instructor may wish to reassure them on
the following points: (a) the distinction between Y and y in Section 2.1 is for clarity only;
(b) for an exercise requiring a grouped frequency distribution, there are many different
"right answers"; (c) the material on histograms with unequal class widths is for
"consciousness-raising" purposes -- the exercises do not require students to create such
histograms.
Comments on Sections 2.4 - 2.6
This is an opportunity to get students started using their calculators effectively. Two
useful general principles are:
(a) Minimize roundoff error by keeping intermediate answers in the calculator rather
than writing them down. Round the answers only at the end of the entire
computation. (The topic of how far to round when reporting the mean and SD is
discussed in Section 6.2; for use in Chapter 2, the instructor may wish to give students
a temporary answer, such as "always round to four significant digits.")
