Psyc 450 Lab Homework #4

Psyc 450 Lab Homework #5

Walk-Through:

Using the clinical_kxkMG_2009.sav dataset…

Stress effects different “kinds” of people differently! This study looked at how the “normal” stressors of the scholastic semester differently effected “traditional” and “older” students.

The hypothesis was that while there would be no difference between these groups at the beginning of the semester, “older” students would show greater increases in stress during the semester, than would “traditional” students, resulting in much higher stress levels among “older” students during the end of the semester.

Portray that hypothesis below.

Does your portrayal predict an interaction?

Does your portrayal predict a main effect for Semester? Is that main effect expected to be descriptive or misleading? Please explain your answer carefully.

Does your portrayal predict a main effect for Group? Is that main effect expected to be descriptive or misleading? Please explain your answer carefully.

Interaction: F = ______df = ____, ______MSe = ______p = ______

N = _____ k = ______n = ______LSDmmd = ______

Is the interaction effect causally interpretable? Why or why not? Could you conduct this study so that the interaction were causally interpretable? Carefully explain your answer.

Describe the pattern of the interaction:

The research hypothesis actually gives both sets of simple effects.

What parts of the research hypothesis relate to the simple effects of group at each time?

What parts of the research hypothesis relate to the simple effects of time for each group?

Which of these is directly tested by the LSD analyses just above?

Do these results support the RH:? Why or why not?

Main effect of Semester F = ______df = ____, ______MSe = ______p = ______

N = _____ k = ______n = ______LSDmmd = ______

Is the main effect of Semester causally interpretable? Why or why not? Could you conduct this study so that the interaction were causally interpretable? Carefully explain your answer.

To determine if the pattern of the Semester main effect is descriptive or misleading, we will need to look at the simple effect of Semester for each Group, using the results from the interaction analysis.

What LSDmmd will you use ______

Describe the pattern of the main effect of Semester (including whether that main effect pattern is descriptive or misleading).

Which part of the research hypothesis is tested with this main effect? Does this pattern support that part of the research hypothesis? Why or why not?

Main effect of Group F = ______df = ____, ______MSe = ______p = ______

N = _____ k = ______n = ______LSDmmd = ______

Is the main effect of Group causally interpretable? Why or why not? Could you conduct this study so that the interaction were causally interpretable? Carefully explain your answer.

To determine if the pattern of the Group main effect is descriptive or misleading, we will need to look at the simple effect of Group for each portion of the Semester.

What LSDmmd will you use ______

Describe the pattern of the main effect of Group (including whether that main effect pattern is descriptive or misleading).

Which part of the research hypothesis is tested with this main effect? Does this pattern support that part of the research hypothesis? Why or why not?

On Your Own

Using the examprep_kxkMG_2011.sav dataset…

The purpose of the study was to look for differential performance over time by those who completed individual vs. group Exam preparation assignments. Data were obtained from two successive semesters of a History of Psychology course. The course included three exams, each of which was preceded by a preparatory assignment designed to review the key issues covered during that portion of the course. During the Fall semester each of these assignments was completed individually by each student. During the Spring semester each of these assignments was completed in groups of three students. The outcome variables were the % scores from each of the three exams. The data are available from the website homework.sav

a.  Write the cell and marginal means into the table above.

b.  For the interaction F ______df ____, ______MSerror ______p ______r ______

k ______n ______LSDmmd ______

c.  SE of Exam for each Preparation Type: use <, > & = to indicate the RH: and the results based on LSD for each pairwise comparison. Also compute the effect size and indicate whether or not the RH: is supported for each.

d.  SE of Preparation Type for each Exam: Use <, > & = to indicate the results based on LSD for each pairwise comparison. Also compute the effect size.

e.  Is the RH3: about the interaction supported?

Is the RH3: about the interaction supported

f.  For the Exam main effect F ______df __, ____ MSerror ______p ______r ______

k ______n ______LSDmmd ______

g.  ME of Exam Use <, > & = to indicate the results based on LSD for each pairwise comparison. Also compute the effect size

h.  Is the main effect of Exam descriptive or misleading?

i.  Is the RH: about the main effect of Exam supported?

j.  For the Preparation Type main effect F ______df ____, ____ MSerror ______p ______r ______

k.  Is the main effect of Preparation Type r descriptive or misleading?

l.  Is the RH: about the main effect of Preparation Type r supported?

Write up the results, following the example in the SPSS handouts

·  include a table and a graph

·  incorporate whether or not there is support for the thee RH: (be sure to use the right SE to describe the interaction RH:)

·  include effect sizes for each F-test and pairwise comparison