Practice 11

1. One-Way ANCOVA . Go to www.ablongman.com/george9e and click on the "Data Sets" link at the top of the page. Download the grades.sav file. You will need to open the file in SPSS to complete this assignment.

( Note : Use the gpa, extcr, and total variables for this assignment.)

1. List the variables and explain their scale of measurement (nominal, ordinal, interval, or ratio).
   
2. You are told that this data set represented the following study: "Participants were given the opportunity to do an extra credit project in the course. The instructor suspects that those who do the extra credit project will learn more and do better in the course, as observed by their total score. Because students who tend to have higher GPAs are likely to do well in classes overall, we would like to control for this variable in our analysis." What are the independent and dependent variables, and the covariate, in this study?
   
3. What is the mean, median, mode, range, standard deviation, and variance for gpa and total?
4. What are the null and alternative hypotheses for the study? Provide the statistical notation and written explanation for each.
5. Complete the following ANOVA table based on the results obtained from SPSS (not all cells require a number), when the covariate is NOT included:
   Summary of one-way ANOVA of total grade

   Source	SS	df	MS	F	p
   Between groups	2151	1	2151	9.985	.002
   Within groups	22192	103	215
   total	24343	104

6. Complete the following ANOVA table based on the results obtained from SPSS (not all cells require a number), when the covariate is included:
   Summary of one-way ANCOVA of total grade

   Source	SS	df	MS	F	p

7. What differences did you find when including the covariate? Explain.
8. Why did we run an ANCOVA on this data set? Why is this considered a one-way ANCOVA?
9. What is the main effect and is it statistically significant? How do you know?
10. Should you conduct a post-hoc test on the means? Why or why not? If so, after conducting the test, which means are significantly different from each other? How do you know?
11. What conclusion might you draw from all of these results? Do we retain or reject our null hypothesis? Explain. (Please see George and Mallery (2009), bottom of page 159, for examples of how to present results for ANOVA tests in sentence format and including the necessary statistics.)

1. Attach the output file to your post:

1. Use the instructions in George and Mallery (2009) to obtain the frequencies, mean, range, standard deviation, and variance for gpa and total. ( Note : You will need the frequencies to determine the median and mode.)
2. Run the one-way ANOVA, ANCOVA, and Tukey’s HSD using the instructions in George and Mallery (2009).
3. Clean up the output file created and then save it as a spv file to your computer.

GLM-multovariate- cov-GPA, DV- test score. Fixed- extra credit. Post hoc, desc. Stats, plots. Plot- estimated marginal means- move over EC.

Practice 12

1. Model Building or Logistic regression . Go to www.ablongman.com/george9e and click on the "Data Sets" link at the top of the page. Download the divorce-studentversion.sav file. You will need to open the file in SPSS to complete this assignment.

( Note : For this assignment, only focus on the following variables: ddepre, dfeel1, dfeel2, dfeel3, dlower, ddisr1, ddisr2, dloss, dlack, dlegal, dfinan, dchild, and lsatisy. Each variable is measured using a psychological measure, where the higher the score on the test represents more of that variable. You want to build a model to predict lsatisy using a combination of these predictors.)

Analyze-regression-binary logistic- DV:lsatisy, cov:all other

1. List the variables and explain their scale of measurement (nominal, ordinal, interval, or ratio).
2. What is the mean, median, mode, range, standard deviation, and variance for all variables?
3. What are the different correlation coefficients? Describe what you know about each correlation based on the coefficients obtained.
4. Use the backward elimination, forward selection, or stepwise regression procedure to build your model.

1. Describe the procedure chosen and why it was chosen for building this model.
2. Which variable has the highest correlation with lsatisy and should be used first in building the multiple regression model?
3. What is the multiple correlation coefficient? What does this tell us about the first predictor added to the model?
4. Complete the following chart, using as many steps as needed until the R ² no longer changes significantly:

1. What is the regression equation for the model you obtained from the regression procedure to predict lsatisy?
2. Make four predictions for lsatisy (Y) based on made-up scores for all variables included in your regression equation:

1. lsatisy =
2. lsatisy =
3. lsatisy =
4. lsatisy =

1. What is the F statistic for the chosen model? Is it significant? How do you know and what does this tell us?

1. Attach the output file to your post:

1. Use the instructions in George and Mallery (2009) to obtain the frequencies, mean, range, standard deviation, and variance for all variables. ( Note : You will need the frequencies to determine the median and mode.)
2. Run the correlation and regression analyses using the instructions in George and Mallery (2009).
3. Obtain a scatterplot with the regression line by going to Analyze Regression Curve Estimation and choosing your variables.
4. Clean up the output file created and then save it as a spv file to your computer.

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