Introduction to Statistics in Psychology: PSY 201 Greg Francis, PhD Department of Psychological Sciences Psychological Sciences Building, Room 3186, (765) 494-6934 email: gfrancis@purdue.edu http://www.psych.purdue.edu/∼gfrancis/Classes/PSY201/index.html Study Guide for Exam 3 Exam Date: November 23, 2015 (during the regular class period) The exam will consist of 10 short-answer questions that will either involve some computation or will require a short essay to explain a concept in statistics. Drawings, graphs, and examples are often helpful when answering an essay question. For computations, you can receive partial credit as long as you show your work. Bring a calculator. For this exam, you should prepare an “information sheet” that you can bring with you to the exam. On a single 8.5 × 11 sheet of paper, you can write (hand written only) anything you think might be helpful. You can use both sides of the paper. Since any information you need can be on your sheet, the exam will not include a listing of equations. NEW: You will have the option to partially replace your score on Exam 2 with the score on Exam 3. On the front page of Exam 3 will be a box. If you check the box, your current Exam 2 score will be replaced by the average of your old Exam 2 score and the score you earn on Exam 3. Thus, if you think you have done better on Exam 3 than on Exam 2, you should check this box. If you think you have done worse on Exam 3 than on Exam 2, you should leave the box unchecked. Chapter 9 1. Know how to interpret the probability value in a hypothesis test. 2. Know how to set up and interpret a null hypothesis. Understand its relationship to chance. 3. Understand what it means to reject the null hypothesis. 4. Understand the difference between statistical significance and practical significance. 5. Know the definitions and properties of Type I and II errors. 6. Understand the differences between one-tailed and two-tailed tests. Understand how the probability is calculated in each case. 7. Know how to interpret a non-significant result. 1 8. Know the steps of hypothesis testing. 9. Know the relationship between significance testing and confidence intervals. 10. Understand the common misconceptions about significance testing and the proper interpretation. Chapter 10 1. Know how to perform a hypothesis test for a single mean when the population standard deviation is unknown. 2. Know how to perform a hypothesis test for the difference of two independent means when the standard deviation is unknown. Be able to do the test for unequal sample sizes. 3. Know what assumptions are needed to do the hypothesis test for the difference of two independent means when the standard deviation is unknown. Know what happens to the Type I error rate when these assumptions are violated. 4. Understand the effect of doing multiple t tests among all pairs of means on the Type I error rate. 5. Be able to calculate the Tukey honestly significant difference (HSD) test for unequal sample sizes. 6. Understand the issues of testing linear combinations of means. Be able to set up coefficients for simple cases. Be able to run the significance test (for equal sample sizes only). Do not worry about “orthogonal” comparisons. 7. Understand, in general, what the Bonferroni correction is about. 8. Be able to perform a hypothesis test for the difference between dependent means (correlated pairs). 9. Be able to perform specific comparisons for correlated observations. Chapter 11 1. Understand what power is. Be able to properly describe it as a probability. 2. Understand how to compute power from the binomial distribution or the normal distribution. 3. Understand the factors that affect power. Chapter 14 1. Know, in general, how the χ2 distribution changes with degrees of freedom. 2. Know how to set up a null hypothesis for a one-way table. 2 3. Know how to compute the Ei and Oi terms for a one-way table. Know how to compute χ2 . 4. Know how to compute the degrees of freedom for the χ2 value for a one-way table. 5. Know how to use the on-line calculator to get the p value for a χ2 test. 6. Understand how a one-way table χ2 test can be used to test for deviations from a distribution shape. 7. Know how to set up a contingency table for a χ2 test. Know how to compute χ2 for this case. 8. Understand, in general, the limitations of the χ2 test. 3