Assignment 5 t test and ANOVA 4Conducting Tests In Activity #4 you learned how to examine relationships between variables, conduct analyses related to correlation and regression, and interpret the output associated with each. In this section you will learn how to conduct tests that determine if there are differences between mean scores for groups. For example, you might be interested in studying whether there are mean differences in heart rate between two groups: those who exercise and those who do not (t-test), or you might a slightly more complicated design and compare mean heart rates for three groups: non-exercisers, occasional exercisers, and regularly exercisers (ANOVA). To Prepare for Activity #5: Download SPSS Data Sets. • Activity 5a.sav (found on the “additional resources” page) • Activity 5c.sav (found on the “additional resources” page) NOTE: You may experience an error message when attempting to run the analysis using SPSS of the .sav file used in this assignment. The error message says: Warnings Command name: DESCRIPTIVES Input error when reading a case. This command not executed. If you experience this error, click on the data view tab of the opened .sav file, then click on the line separating the labels of the first and second column. Drag the width of the first column out approximately 25% from its initial width. Save the file. The analysis should now work as intended. Read Chapters 9 and 10 in the text. It will be to your advantage to have SPSS open on your computer as you work through chapters 9 and 10. While you are reading through this chapter and testing the assumptions of various statistical procedures, consider various types of datasets and whether they would run the risk of violating these assumptions. Complete the Self-Tests within each chapter. Answers are available on the companion web site under the heading Additional Web Material in the Student Resource section (http://www.sagepub.com/field3e/additionalwebmaterial.htm). Complete Smart Alex’s Quizzes. Be sure to take Smart Alex’s Quiz at the end of the Chapter and spend time learning the concepts related to questions you answered incorrectly. Answers are available at: http://www.sagepub.com/field3e/SmartAlexAnswers.htm Optional Preparation for Activity #5 After completing the above activities, if you feel you need additional instruction on the concepts covered, please choose from any of the following activities that will assist you in mastering the core concepts. Interactive Multiple Choice Questions. You might find it helpful to complete the multiple choice quizzes available at: http://www.sagepub.com/field3e/MCQ.htm Flashcards. If what you need is gain a basic, definitional understanding of the topics, visit the Flashcard Glossary at: http://www.sagepub.com/field3e/Flashcard.htm Activity #5 You will submit one Word document and one SPSS data file for this activity. You will create the Word document by cutting and pasting SPSS output into word. Please read the instructions below to ensure you are pasting the correct material into your activity document. The Word document will be named LastnamefirstinitialSTAT8028-5a and the SPSS document as -5b. Part A. Dependent t-test In this activity, we are interested in finding out whether participation in a creative writing course results in increased scores of a creativity assessment. For this part of the activity, you will be using the data file “Activity 5a.sav”. In this file, “Participant” is the numeric student identifier, “CreativityPre” contains creativity pre-test scores, and “CreativityPost” contains creativity post-test scores. A total of 40 students completed the pre-test, took the creativity course, and then took -test. 1. Exploratory Data Analysis/Hypotheses. a. Perform exploratory data analysis on CreativityPre and CreativityPost. Using SPSS, calculate the mean and standard deviation of these two variables. b. Construct an appropriate chart/graph that displays the relevant information for these two variables. c. Write the null and alternative hypotheses used to test the question above (e.g., whether participation in the course affects writing scores). 2. Comparison of Means a. Perform a dependent t-test to assess your hypotheses above (note that many versions of SPSS use the term “paired samples t-test” rather than dependent t-test; the test itself is the same. b. Write one or two paragraphs that describe the dataset, gives your hypothesis, and presents the results of the dependent sample t-test. Be sure that your writing conforms to APA style. Part B. Independent t-test In this activity, we will start with the data file used in Part A (“Activity 5a.sav”). Suppose, however, you [the researcher] encountered a small problem during data collection: after -tests were collected, you realized that -test form did not ask for the students’ identification number. As such, it will be impossible to match pre-test scores to post-test scores. Rather than simply give up, you start thinking about the data you do have, and try to determine whether you can salvage your project. In assessing the situation, you realize that you have 40 pre-test scores and 40 post-test scores, but no way to link them. While it will result in a weaker comparison, you determine that you are still able to compare pre-test vs. post-test scores; you will use a between-subjects design rather than a within-subjects design. 1. Create the data set. a. Using the “Activity 5a.sav” file as a starting point, create a new dataset that you can use with the between subjects design. Hint: you will no longer need the variables CreativePre and CreativeTest. Instead, you have only one variable for the score on the creativity test. A second (or grouping) variable will serve to indicate which test the student took. b. Submit the dataset as one of the Activity 5 files. 2. Exploratory Data Analysis/Hypotheses. a. Perform exploratory data analysis on CreativityPre and CreativityPost. Using SPSS, calculate the mean and standard deviation of these two variables. b. Construct an appropriate chart/graph that displays the relevant information for these two variables. c. Write the null and alternative hypotheses used to test the question above (e.g., whether participation in the course affects writing scores). 3. Comparison of Means a. Perform an independent t-test to assess your hypotheses above (note that many versions of SPSS use the term “independent samples t-test” rather than simply “independent t-test”. b. Write one or two paragraphs that describe the dataset, gives your hypothesis, and presents the results of the dependent sample t-test. Be sure that your writing conforms to APA style. 4. Comparison of Designs a. In this activity you used the same dataset to analyze both a between- and within-subjects design. Create a single paragraph (using the material you wrote above), that presents both sets of results. b. Explain, in 300-500 words, whether the two tests resulted in the same findings. Did you expect this to be the case? Why or why not? What have you learned in this activity? Part C. ANOVA All of us have had our blood pressure measured while at our physician’s office. How accurate are these measurements? It may surprise you to learn that there is something called “White coat syndrome”—the tendency of some people to exhibit elevated blood pressure in clinical (medical) settings only. In other words, for these people the very fact that the physician is taking their blood pressure causes it to increase (for more information about white coat syndrome see http://www.webmd.com/anxiety-panic/features/beyond-white-coat-syndrome). In this activity, you will be using the “Activity 5c.sav” data file to determine whether you find support for the existence of white coat syndrome. In this study, 60 participants were randomly assigned to one of three groups. The “settings” variable indicates the location in which the participant’s blood pressure was recorded: 1=home, 2=in a doctor’s office, and 3=in a classroom setting. The “SystolicBP” variable contains the participant’s systolic pressure (the “upper” number). The “DiastolicBP” variable contains the participant’s diastolic pressure (the “lower” number). 1. Exploratory Data Analysis/Hypotheses. a. Perform exploratory data analysis on both the SystolicBP and DiastolicBP variables. Using SPSS, calculate the mean and standard deviation of these two variables. Be sure that your analysis is broken down by setting (e.g., you will have six means, six SD’s, etc.). b. Create two graphs—one for systolic and one for diastolic pressure. Each graph should clearly delineate the three groups. c. Write a null and alternative hypothesis for the comparison of the three groups (note that your hypothesis will state that the three groups are equivalent; be sure to word your null hypothesis correctly). 2.ANOVA. a. Using the “Activity 5c.sav” data file, perform two single factor ANOVAs: one using SystolicBP and one using DiastolicBP as the dependent variable. b. If appropriate for either or both of the ANOVAs, perform post hoc analyses to determine which groups actually differ. c. Write one paragraph for each ANOVA (be sure to use APA style). At a bare minimum, each paragraph should contain the three means, three SD’s, ANOVA results (F, df), post hoc tests (if applicable), effect size, and an interpretation of these results.
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