Psychology 315

Understanding Statistics in Psychology

Introduction

Please read these introductory pages. The information will help you successfully complete this course.

Course Objectives

Psychology 315 is an introductory course in applied statistics, with particular emphasis in psychology. Both descriptive and inferential statistics are included, and the course is equivalent to the on-campus version of this course. In addition, this course provides the basic statistical background and understanding needed prior to enrollment in the undergraduate psychology laboratory courses.

By the end of this course, you should be able to

• evaluate scientific hypotheses using an appropriate statistical inference test;
• read original experimental literature with a better understanding of the research design and data analysis; and
• engage more meaningfully in your own research.

This course includes important basic research design and analysis concepts and many statistical inference tests, but unlike the Psychology 317/318 course, does not include methods for analyzing complicated experimental designs or an in depth study of probability. Special mathematical competence, beyond basic algebra, is not required for successful completion of this course. Lesson One covers the prerequisite mathematics.

About the Online Environment

Your online course offers several advantages to the traditional classroom, including the comprehensive Online Student Handbook, the ability to communicate electronically with students and with your instructor, and links to a rich array of online resources.

Online Student Handbook

This handbook answers questions about your online learning course, such as how to purchase your text, schedule an exam, obtain a transcript, and get technical help if you need it. The handbook also provides additional resources, such as how to order books or journals from the library and how to study for an online course.

Communication with Your Instructor and Student Peers

• Online Discussion Forums, designed by the University of Washington award winning Catalyst team, allow you to communicate with other currently enrolled students and with your instructor. We encourage you to use the forum to exchange ideas, resources, and comments about your course work with other students in this course. This unstructured forum is monitored by your instructor.
• You can use e-mail to ask me a question or preferably post your question in the forum. I will reply there.

Online Resources

As an online student, you have access to a wealth of Web resources compiled to provide fast, easy access to information that supports your online learning experience. Organized by subjects, Online Resources link you to sites with help for writing and research, study skills, language learning, and library reference materials. All links have been assessed for credibility and reliability, and they are regularly monitored to ensure their usability.

Written Assignments

Each lesson (other than exams) consists of a reading assignment from your text and its accompanying Study Guide, and a written assignment to be submitted for instructor feedback. Some lessons include an Excel assignment to be submitted for grading. Every third lesson is an exam. The first lesson includes a Student Information Sheet. Please submit it with the first lesson. Be sure to include phone number(s), e-mail address, etc. so that I will have a way of contacting you if necessary.

In general, the written assignments include practice problems and end-of-chapter problems from the text, and true-false questions and self-quizzes from the Study Guide. Answers to all the Study Guide questions can be found at the back of the Study Guide. Answers to selected end-of-chapter problems are in the back of the text. Although you should work all of the assigned written material, you only need to send in the answers to the end-of-chapter problems from the text and the Excel assignments. You may, of course, include additional problems from the rest of the assignment (i.e., the study guide) if you need help getting correct answers.

Please follow the guidelines below, in preparing written assignments.

1. Please write neatly and legibly on one side of the paper only. All work may be done in pencil, pen, or computer (not recommended for calculation problems).
2. Leave ample space on the left or the right for corrections or comments. For calculation problems show your work. That is, include all essential steps in solving the problem so the instructor can follow your solution and find any errors.
3. Answers should be clearly indicated by setting them off in some way, such as by circling, highlighting, underlining, setting off in brackets, etc.
4. When you cannot solve a problem, leave space under the number of the problem for the instructor to provide the solution. (Of course, you may always contact the instructor for help prior to submittal of the assignment).
5. Final answers should be rounded to the same number of digits as used in the text for that material. For example, probability problems are, by convention, rounded to four decimal places, whereas most other types of problems are rounded to only two decimal places. Always carry intermediate calculations to at least two more decimal places than the number of places planned for the final answer. For example, if the final answer is rounded to two decimal places, carry the intermediate calculations to at least four decimal places. You must follow this policy and also follow the rounding rules as presented in the text, or you will not get the answers given in the back of the text.

If an assignment is extremely poor and/or if the instructor believes you will benefit from doing all or part of it over, you will be asked to do so. In that case, re-submit the new solutions after completion.

Written assignments, with the exception of Excel assignments, will be graded pass/fail. They will not "count" directly toward your final grade, but they will give you important practice and instructor feedback that is very likely to help you earn a better grade in the course. Excel assignments will be graded. The point value of each assignment is noted in the lessons in which they occur.

Calculators

Calculators should be used in doing computational problems. The calculator you use for this class must have statistical functions. Most inexpensive calculators have the functions you will need. You must be able to enter a set of numbers and then easily recall from memory the following terms, the mean,  X,  X² and n (sample size). These memory and statistical functions will make it easier and much faster to do the necessary calculations as you progress through the course. You should plan on using the same calculator throughout the course. In other words, you should not attempt to learn how to use a new calculator just prior to an exam!

Instructor Recommended Study Strategy

Successful completion of this course requires dedication to a sound study plan. You should try to complete one lesson per week. If you are having trouble, rather than put the work aside, contact me for help. The material in this course builds on itself, so long delays between assignments will be very detrimental to learning. In order to "get the most out of assignments" and enhance test performance, the following study steps are highly recommended.

1. Carefully study the text and the Study Guide until you understand the concepts and can do the illustrative and practice problems. Always do the practice problems immediately after the appropriate section of text. Work the practice problems on your own and then check to see if you did the steps correctly.
2. After completion of step 1, work the homework problems. You should be able to complete most of them by using the appropriate formula, and without repeatedly referring back to the text. The homework should provide you with practice applying concepts from the corresponding chapter and can serve as a "practice" exam of sorts.
3. Many homework answers are in the back of the text. Check your homework answers after you have completed one, or several problems. However, do not use the answers in the back as a regular means of determining how to actually do homework problems. If you find yourself looking up answers and then trying problems several different ways until you finally get the correct answer, this should indicate to you that your understanding of the material is insufficient. Remember, on exams, answers are not provided. If you are having trouble, review the relevant concepts in the text and/or contact me for help. Often a brief e-mail interaction or a short phone call with the instructor can prevent hours of frustration.
4. Send your written assignment to me. When the assignment is returned to you, study the corrections and comments carefully.
5. Please do not attempt to wing it on exams. Contact me for help if there are still concepts or problems you do not clearly understand.

When Your Answer Doesn't Match the One in the Text

If your answer doesn't match the one in the text, first look over your work for simple clerical or calculation errors. If you don't find any errors, check to make sure that mathematical substitutions into the formula were correct. For example, did you use  X², instead of  X? If you still can't find the error, and most of your other homework is correct, send in the assignment, leaving room for the instructor to show you the solution.

Please don't spend several hours on one problem, trying to arrive at the answer given in the text. If you've calculated an answer repeatedly (starting from the very beginning of the problem) and you are reliably getting the same incorrect answer, stop. You are probably making the same error repeatedly. Common errors include copying numbers incorrectly from the text, applying rounding rules incorrectly, or forgetting to take a square root.

Examinations

All exams will have a 2-1/2 hour time limit. You will not be allowed to use your books or notes, but tables and equations will be provided (you do not have to memorize equations). Bring your calculator—it will be necessary. Practice exams are contained in the appendix of the syllabus. On computational questions, show all steps to the final answer, beginning with the equation used and a term-by-term substitution into the equation. Even if you use an advanced calculator, you must show the original equation and the term-by-term substitution in order to receive credit on the problem. Partial credit is given on computational problems.

How You Will Be Graded

There are four examinations for this course. The exams are all weighted equally. They are each worth 100 points, with an opportunity for extra credit points on some exams. There are three Excel assignments worth a total of 50 points altogether. In addition to extra credit opportunities on exams, there is also the opportunity to earn five extra credit points by completing the assignment described below. Your homework assignment evaluations will not be used in determining your final grade per se. It is expected that successful completion of homework will greatly enhance performance on exams. Your final grade will be based on the average of your exam scores and Excel assignments, including the points for the extra credit assignment (if you elect to complete it) and any points for correct completion of extra credit problems on exams.

To calculate your course average, add all your points earned including exam scores, Excel points and extra credit. The maximum total points without extra credit is 450. Therefore, in order to determine your course average, divide your total points earned (including extra credit) by 450 and then multiply by 100. Find your corresponding GPA in the following table.

Average	GPA	Average	GPA	Average	GPA	Average	GPA
100–99	4.0	89	3.5	79	2.5	69	1.5
98	4.0	88	3.4	78	2.4	68	1.5
97	4.0	87	3.3	77	2.3	67	1.4
96	3.9	86	3.2	76	2.2	66	1.3
95	3.9	85	3.1	75	2.1	65	1.2
94	3.8	84	3.0	74	2.0	64	1.1
93	3.8	83	2.9	73	1.9	63	1.0
92	3.7	82	2.8	72	1.8	62	0.9
91	3.7	81	2.7	71	1.7	61	0.8
90	3.6	80	2.6	70	1.6	60	0.7

Extra Credit

Take a moment now and read the "Extra Credit" section in Lesson Eleven. As indicated, you can earn up to five extra credit points on the fourth exam by writing an analysis of a newspaper article or advertisement, showing how the proper use of inferential statistics would improve the article. You should be on the lookout for such an article so that when you get to Lesson Eleven, you can get the extra credit. Your analysis should be like the "What is the Truth" sections that appear at the end of some of the textbook chapters.

Course Options

In order to give you greater control over your learning experience, this course has been structured so that you can choose either to work under close instructor supervision, submitting each assignment for instructor feedback as described above, or to move ahead at your own pace. You may choose one of two options.

Option One

As designed and described above, the student who elects this option will submit all written assignments sequentially, waiting to receive evaluation on each assignment before submitting the next. This is the approach that the majority of students select, and the one the instructor recommends for most students. In general, students tend to learn more and earn higher grades if they systematically submit each assignment and receive instructor feedback before moving ahead.

Students who are confident of their math skills and knowledge of the material may save up assignments and submit them in "batches" before each exam, rather than submitting each assignment and waiting to get it back before submitting the next. For example, the student may submit Assignments 1 and 2 together, prior to exam 1. This can cut down on the time that is normally needed to grade and return each assignment. You may not, however, submit any assignments that follow the next exam (e.g., do not submit Assignment 4 prior to taking exam 1). You must not send assignments in batches if you cannot do all the homework on an earlier assignment. For example, if you cannot do all the homework in Assignment 4, you should send it in for feedback prior to doing Assignment 5—thus sending Assignments 4 and 5 as a batch would not be possible.

Option Two

If you choose this option you will be submitting only the Excel assignments and taking the exams. The student who elects this option will be choosing minimal instructor feedback. The student should work through all assignments independently, but need not submit them to the instructor, with the exception that Excel assignments must be submitted. Excel assignments are graded and points are included in the final grade. Each examination should be requested when the student has studied the relevant material, is ready to take the exam, and is willing to accept responsibility for his or her own judgment as to readiness.

The advantage of this option is that a strong and independent student can pace their own progress in the course and significantly reduce the time required for submittal of assignments and receipt of instructor feedback. However, this option is recommended only for the very few students who have extremely good math and analytical thinking skills. It is highly recommended that the student do each assignment as carefully as if it were going to be submitted for grading. It is unlikely that any student will do well on the exams without having done the homework. The answers to most of the end-of-chapter problems are given in the appendix to the text. If you elect not to turn in end-of-chapter problems for evaluation, I strongly suggest that you check your own answers.

If you select Option Two, please note, that once you have taken an exam, you cannot elect to back up and redo that portion of the course with Option One, in an effort to better your grade. Your exam grade will stand. You can, however, begin the course under Option One and change to Option Two at any point. You can also elect to begin any subsequent portion of the course using Option One even if you have already done part of the course under Option Two.

A Few Words of Encouragement

Students are often concerned that this course will be too difficult for them because of the math content. However, basic algebra and a statistical calculator are all that are really needed. In fact, usually over 50 percent of students earn an A or B grade.

For many students, the conceptual material is actually the more difficult part of the course. Clarification of both conceptual and mathematical material is readily available to you by contacting me. I am available for extra help by phone, e-mail and/or will happily make an on-campus, in person, appointment with you.

About the Course Developer

Nona Phillips

I received my Ph.D. in developmental psychology from the University of Washington in 1984. I am currently a member of the UW Department of Comparative Medicine. Over the years I have taught this Psychology Statistics course many times, both in on-campus lecture format and through Distance Learning. My past research focused on studies of the effects of prenatal exposure to anti-epileptic medications on infant postnatal development. I am currently the Director of the UW Office of Animal Welfare.

About the Author

This course was originally designed by Emily Dibble while completing her doctoral work at the University of Washington. It has since been revised several times by Nona Phillips, to reflect changes in newer editions of the textbook.

Errata

This edition of the textbook is brand new. Please make note of the errors found to date. If you find additional errors, please notify me so that the errors can be included below in subsequent editions of this document.

1. On page 359, there is an error in the decision rules stated for ANOVA. It should read:
   
   If F_obt ≥ F_crit, reject H₀
   
   If F_obt < F_crit, retain H₀
2. On page 510, there is a typo in the answer to problem #4 for Chapter 2. The word "ordinal" in line 3 should read "interval."

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