STAT 310 – Assignment #6 ~ Kruskal-Wallis Test and Analysis of Data from Randomized Complete Block Designs (22pts.) (Due 3/21/08)
1 – Efficacy of Using a Virtual Kitchen for Vocational Training of People with Learning Disabilities
The objective of a study by Brooks et al. “An Evaluation of the Efficacy of Training People with Learning Disabilities in a Virtual Environment” (Disability and Rehabilitation, 2002), was to evaluate the efficacy of using a virtual kitchen for vocational training of people with learning disabilities. Twenty-four students participated in the study. Each participant performed four food preparation tasks and they were scored on the quality of the preparation. Then each participant received regular vocational training in food preparation (real training), virtual training using a TV and computer screen of a typical kitchen, workbook training with specialized reading materials, and no training (to serve as control). After each of these trainings, the subjects were tested on food preparation. Improvement scores for each of the four training methods were recorded and the final results are contained in the file: Vocational Disabilities.JMP.
a) Because the abilities of the 24 students varied substantially, the students will serve as blocks in this study. Was blocking effective here? Explain. (2 pts.)
b) All students received each of the methods of training (or lack of in the case of the control condition). Should all students receive the different training methods in the same order? If not, what should be done in terms of ordering? (2 pts.)
c) Do you see any problems with all four training methods being used for all subjects? Explain. (2 pts.)
d) Is there evidence to suggest that the mean improvement scores differ across the different training methods? Conduct an appropriate test and summarize your findings. Be sure to check assumptions. (4 pts.)
e) Use multiple comparisons to the compare mean improvement scores between the methods of training. Also find CI’s for the differences in the mean improvement scores between the groups. Summarize these findings in a few well-written sentences. (4 pts.)
2 – Phonemic Awareness Training
A study of young children by Flexer et al. “Using Sound-field to Teach Phonemic Awareness to Pre-schoolers” (The Healing Journal, 2002) examines the effectiveness of FM sound field when teaching phonics to children. In the study, children in the classroom with no phonological or phonemic awareness (control) were compared to a class with phonological and phonemic awareness (PPA) and to a class that utilized phonological and phonemic awareness training and the FM sound field (PPA/FM). A total of 53 students from three separate preschool classrooms participated in this study. Students were given a measure of phonemic awareness in preschool and then at the end of the first semester of kindergarten. Improvement scores on the Yopp-Singer Test of Phonemic Segmentation were recorded for the children in each of the three classroom settings. The results are contained in the file Phonemic Awareness.JMP.
a) Use the Kruskal-Wallis procedure to determine if there is a significant difference in the improvements scores for the three groups. Summarize your findings. (3 pts.)
b) Use the multiple comparisons based on ranks to compare the two experimental classrooms (PPA & PPA/FM) to the control classroom. Summarize your findings. (5 pts.)