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Part I

Guide to the Instructor

Objectives of Tales of Distributions

When Jim Johnston and I began this book project, our principal objective was to write a clear, informal book that did an excellent job of explaining the concepts covered in typical undergraduate statistics courses in psychology and the behavioral sciences. Other objectives emerged as we wrote that first edition. My objectives for this 10th edition include that ambitious one we began with and in addition,

Show how a variety of disciplines use statistics by using contemporary examples

Emphasize interpretation

Promote a few classic studies in social science by using them as problems or examples

Introduce some of the pioneers who developed statistics

Have students choose the correct statistical test, find the right answer, and tell a coherent story based on the statistical analysis

Features of Tales of Distributions

These features help describe Tales and illustrate some ways in which this book differs from other statistics texts.

  1. The most important feature in Tales is the conversational writing style that is both encouraging and engaging, especially for a statistics textbook.
  2. Problemsare interspersed throughout each chapter rather than being clumped at the end. My intention is that students engage in spaced practice rather than massed practice.
  3. All answers to chapter problems are provided and given in detail. More than 50 pages of the book are devoted to answers. Students can check their work immediately.
  4. Both problems and examples in the text come from a variety of disciplines, congruent with the fact that regardless of major, students leave college to work in a wide variety of fields.
  5. Interpretation is emphasized in both the text and the problems. The interpretation headingfor all answers is highlighted.
  6. Experimental design conceptsare woven into the book in many places. This permits interpretations that incorporate the terms of the experiment.
  7. Computer software analyses are illustrated with tables based closely on SPSS printouts.
  8. Important words and phrases are defined in the margin when they first occur.
  9. Every chapter has one or more Comprehensive Problems that encompass most or all of the techniques covered in a chapter.
  10. A set of What Would You Recommend? problems appear after every 4 or 5 chapters. To answer, the student chooses a statistical technique from among those that were covered.
  11. Choosing Tests and Writing Interpretations, the final chapter of the book, has a variety of exercises that help students consolidate what they have learned, regardless of the number of chapters covered in their course.
  12. Objectives for each chapter are listed at the beginning of the chapter. These serve first as an orientation list and later as a review list.
  13. Transition passages are provided at various points in the book where the focus of the material that follows is different from earlier material.
  14. Error-detection techniques appear in boxes. As the name implies, these reveal ways to check computations or to avoid errors.
  15. Clues to the Future, also in boxes, are statements telling the student that some just-covered information is going to come up again later in the book.
  16. Founders of statistics are identified with short biographical sketches incorporated into the text. In addition, the problems that Galton, Pearson, “Student,” Fisher, Spearman, and Quetelet worked on are described.
  17. The Student Companion Websitedoes not require a password. There are multiple choice questions(called the tutorial quiz) and flashcards with definitions. Also, there are links to Chapter 17, Power, whichcan be assigned after Chapter 10 in the text, and to the textbook errata sheet. To get there, go to and click on the link.

Day One in Statistics

Day One has always seemed to me to be the single most important day of any class. On the first day a mood is established. This mood goes a long way toward determining what students do in the next 48 hours. It is up to the instructor to plan the class period so that a mood conducive to learning is established.

In statistics, many students come through the door on the first day of class anxious and afraid. Some of them are neoiconophobiacs—those who have an irrational fear of new symbols. Such students need some immediate success experiences in statistics to encourage them to go on. Words of encouragement help ease their discomfort and fear. Probably the best medicine is stories of other students who have succeeded. Knowledge that others have learned statistics despite their initial feelings reduces anxiety.

Lecture Aids

The quarterly journalTeaching of Psychology is a good source of lecture aids. Both the Forum section and the Methods and Techniques section have material directly helpful to statistics teachers. Two compilations of statistics material published from ToP are the Handbook for Teaching Statistics and Research Methods by Mark Ware and Charles Brewer (2nd edition, 1999) and the Handbook of Demonstrations and Activities in Teaching Psychology,Vol.1: Introductory Statistics, Research Methods, and History by Mark Ware and David Johnson (2nd edition, 2000). Barney Bein’s entry in the Encyclopedia of Statistics for the Behavioral Sciences (2005), titled Sources and Materials for Teaching Statistics, lists and describes books, journals, and a website that have material helpful to statistics teachers. David Lane’s online statistics course is a good source of web-based material. See

Encyclopedias. I find that encyclopedias are good sources of lecture material. Biographies, especially, help personalize statistics. In ascending order of technical writing, three good ones are:

  1. The International Encyclopedia of the Social and Behavioral Sciences (2007)has biographical entries and statistical topics.
  2. The Encyclopedia of Statistics for the Behavioral Sciences(2005) is a four-volume work with topics that range from the introductory to the graduate level. Biographies are included.
  3. Topics in the Encyclopedia of Biostatistics (2005) also range from the introductory to the graduate level but are generally more technical.

Sources of statistical problems. In my opinion there is almost nothing worse than a “naked” problem in statistics—a problem that asks students to work on numbers without saying what the numbers represent or why a grown man or woman would gather such data. Besides being boring, such problems prevent the student from completing the last and most important step in a statistics problem, which is to tell the story of what the data show.

To generate problems and examples fordescriptive statistics problems, I recommend:

The World Almanac

Statistical Abstract of the US

Introductory psychology textbooks

For inferential statistics, look at the studies cited by textbooks in your other courses and journal articles that you find engaging. I am also fond of picking up a recent journal, finding an interesting topic, and creating a data set that mimic the findings of the published study. After I have worked up such a problem for my class, the final result is usually a much simpler version than the original.

Undergraduates identify with studies that are proposed or conducted by other undergraduates. For my statistics tests, I often use the independent projects of students in my Research Methods course. Another excellent source is journals that publish studies by undergraduates. Two journals I have used are:

Psi Chi: Journal of Undergraduate Research

Journal of Psychological Inquiry

Tests

Tests are one of the most powerful ways that instructorscommunicate with students. Instructors may tell students to study graphs, work the problems, and pay attention to names, but if graphs, problems, and names do not show up tests, students’direct their attention toactual test materials. By handing tests back to students and discussing them, an instructor can glean valuable feedback.

The tests that students experience in different courses are quite variable. The students don’t know what to expect in a new course. Being explicit about your expectations (and then fulfilling what are now their expectations) goes a long way in creating a cooperative class.

The test items in Part II of this manual will probably be of help in composing tests. Most items have been tested and many were rewritten on the basis of student feedback. Never-the-less, each item should be read carefully and the answer checked before using it.

A friend of mine who gives good tests uses a rule of thumb in making up a test. After the test is constructed, he sits down and works the test, reading each item and writing out the answer. He figures that the test is about the right length if he can do it in one-third of the time allotted for the students to take the test. In addition, he says, by carefully reading the test, he sometimes discovers ambiguities that he didn’t see before.

How Tales Can Be Used

Teachers of statistics vary greatly in their teaching strategies. With the help of reviewers, I designed Tales soit could be used by teachers with many different approaches. As for myself, my course is a self-paced, unit-mastery course. Tales works beautifully for such a strategy. In addition, it works quite well in a lecture/discussion format, according to colleagues who use that approach.

A Self-Paced, Unit-Mastery Method

This method is based on Fred Keller’s Personalized System of Instruction (PSI). The only lecture in my course is at the first class meeting. It consists of a brief discussion of the general topic of statistics and how statistics fits in with other ways of knowing, an explanation of how the class is taught, and stories of students who have been successful.

Students then study each chapter, getting help if needed from me, an assistant, or from another student in the class. When students feel they are ready, they show up at a class meeting and take a test on the chapter they have been studying. These tests are graded for mastery and are marked, “Credit,”“Credit—but take a supplementary test,” or “No Credit.”“Credit” means that the student should proceed with the next chapter. “Credit—but take a supplementary test” means that the student has not mastered quite all the material. An additional test on the missed material must be taken (but not necessarily before mastering the next chapter). Examples of supplementary tests include the distinction between independent and dependent variables, using z scores, interpreting a correlation coefficient, distinguishing independent and paired-sample designs, and so forth. “No Credit” means that another test covering all the material must be taken on that chapter. Test taking continues on each chapter until a “Credit” paper is written. My concept of mastery is “B+ or better.” Graded tests are returned the same day. Most of my class time is spent writing or revising tests, or assisting individual students who need help.

Grades are assigned according to the number of chapters successfully completed and the grade on a comprehensive review examination. Completion of the first 15 chapters and a score of 85 percent or greater on the comprehensive review earns an “A.” Completion of the 15 chapters and a score of less than 85 percent on the review earns a “B.” Successfully completing the first 13 chapters earns a “C”; completing 12 chapters earns a “D.”

An important advantage of this teaching method is that it reduces the feeling that there is a competitive game between student and teacher—that the student is trying to make a grade and the teacher is trying to prevent it. With this system, the grade is up to the student, and the requirements for that grade are known at the beginning of the course. I used this system for more than 25 years. About 75 percent of the students in my classes earned an “A” or a “B.” The Pearson r between ACT composite scores and grades is .39 (N = 373, p < .001).

The problem that some students have with a self-paced system is procrastination. Because each student proceeds through the course at his or her own rate, the temptation is ever present to put off statistics until this term paper is finished or that lab assignment is turned in. I deal with procrastination several ways. At the beginning of the course, I warn of procrastination and point out that they must pass about one test a week to stay out of the danger zone. I give each student a schedule that will lead to an “A.” I describe the wonderful feeling of being ahead of schedule. I send e-mail, make myself available around the campus, and have been known to make telephone calls.

For me, this system has worked wonderfully well. For you, modification of this method or a completely different method may work better. Your own course objectives and personal preference for teaching methods affect your choice of teaching techniques.

Chapter-by-Chapter Comments

This section covers concepts in each chapter. In some cases, the concepts are ones that my students find difficult; in other cases, the concepts are just ones I want to emphasize. For some topics, I offer tips on presenting them.

Many of the problems in the text and in this Instructor’s Manual provide starting points for lecture material. These problems come from classical studies in psychology; some are ancient, some recent. Even if a problem is not identified in the text as belonging to someone, students recognize that there is a story to be told about the problem. Your telling the background story lets students in on the inside scoop of why the study was conducted.

Chapter 1. Introduction.

The first chapter lays the groundwork for much of the book. The distinctions between descriptive and inferential statistics, populations and samples, and parameters and statistics are, of course, important throughout the book. Often, the technical meaning of these terms is new to students. In a preliminary edition years ago, I noted that population and parameter both start with the letter “p” and that sample and statistic both start with “s.” This was too basic for some students so I eliminated it. The idea might be useful as a minor lecture point.

Identification of lower and upper limits of numbers and the definitions of measurement scales have not been particularly difficult for my students nor has the definitions of the four scales of measurement. For my students, the most difficult concepts in Chapter 1 have been the design concepts: independent, dependent, and extraneous variables. The terms are important throughout the text, and it is necessary that students have a fair grasp of their meaning early in the course. You may need to provide additional help; examples seem to help the most.

Creating an engaging milieu in your classroom (without, of course, ever mentioning the word engaging) is an appropriate goal for the time spent on Chapter 1.

Chapter 2. Exploring Data: Frequency Distributions and Graphs.

For lecture material on graphics, I recommend Tufte’s The Visual Display of Quantitative Information. It is full of powerful examples of excellent graphics and terrible graphics. Both kinds engage a class.

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