The data set for this problem derives from the posture measurement study described in the main body
Question:
a. Assuming that the only important effect is that of Day (i.e., the factors Time and Rater are assumed not to have important effects), state the subject-specific scalar form of a random intercept model for analyzing the above data. In stating this model, make sure to describe the assumptions made on the random effects (including the error term) in the model.
b. State the null hypothesis that there is no significant effect of the factor Day in terms of a statement about parameters in yout model given in part (a).
c. Based on a comparison of averages at the bottom of the table, does there appear to be a meaningful effect of the factor Day? Explain.
d. Describe how the data in the above table need to be reorganized in order for the MIXED procedure to carry out the analysis. (Use the format given in Table 25.2 of Chapter 25.)
e. Based on the computer output provided below, is there a significant effect of the factor Day? Explain by specifying the F statistic, its degrees of freedom, and its P-value appropriate for these data.
f. Based on the computer output, compute the estimate of the (exchangeable) correlation assumed by the model. (The output provides estimates of the variance of the subject-specific random intercept effect and the variance of the error term; you need to combine this information to compute the correlation coefficient estimate.)
g. Use the output to test whether there is a significant random effect for Subjects. If such a test was nonsignificant, why might you be concerned regarding the model that has been fit, and how might you redo the analysis?
Step by Step Answer:
Applied Regression Analysis and Other Multivariable Methods
ISBN: 978-1285051086
5th edition
Authors: David G. Kleinbaum, Lawrence L. Kupper, Azhar Nizam, Eli S. Rosenberg