PSY 550 Final Exam with Answers Graded A+

1. QUESTION: For each of the following examples, explain whether the researcher has made a correct decision or has made a Type 1 or Type 2 error. Explain why. 2. Dr. G rejects the null hypothesis although the independent variable had no effect. 3. Dr. R rejects the null hypothesis when it is false. 4. Although the independent variable had an effect, Dr. E does not reject the null hypothesis Your Answer: 1. Type I error is made when we reject the null hypothesis, but the null hypothesis is actually true. This problem would be a type I error because there is no proof that shows that the null hypothesis was false. Dr. G rejected the null hypothesis without knowing if the null hypothesis is false. 2. This would be a valid choice as Dr. G is rejecting a hypothesis that is false. We are to reject the null hypothesis if it is false and in the given scenario it is false. 3. The independent variable had some effect; however, Dr. G does not reject the null hypothesis. When this happens, it is a Type II error. A type II error is akin to a false positive. 2. QUESTION: Explain the value of reversal designs (ABA designs) in single-case research. Your Answer: Reversal designs are usually conducted in applied areas of research in order to investigate solutions that can be beneficial to either individuals or to society. The design can be used to apply treatments that benefit participants and verify the effects of the independent variable by "reversing" the roles. In a reversal design, a single participant is observed prior to (A), during (B), and after (A) a manipulation or treatment. 3. QUESTION: Explain how a one-way analysis of variance works. How do you use betweenand within-group variability? Your Answer: • A one-way analysis of variance is used when the investigator is looking to understand if there are significant differences between the means of three or more independent groups. • Between group variability is used to look at the differences among two or more different groups and how the groups are different from one another. • Within-group variability looks at the differences among members that are a part of the same group.4. QUESTION: After watching nursery-school children, Ken Garoo wants to test the hypothesis that some toys are more fun to play with than others. He decides to compare “fun” toys (blocks) with “unfun” toys (stuffed animals). He also wishes to see if there is a sex difference, as well, so sex is added as an independent variable. A) What kind of design is needed? B) Diagram it out. C) Assuming 20 subjects are needed per cell, how many subjects are needed for this study? ANSWER A) The type of design required for this example would be a 2x2 factorial design. This type of design is needed because we will be able to test the factors within one sample. Using the 2x2 Factorial Design would allow the researcher to test different combinations between each other such as fun toys with males and fun toys with females, and unfun toys with females and unfun toys with males.