Date: Wed, 23 Oct 2002 08:51:23 -0700 Reply-To: "McCrea, Pat A EDUC:EX" Sender: "SPSSX(r) Discussion" From: "McCrea, Pat A EDUC:EX" Subject: Mann-Whitney test: relationship between parental satisfaction an d student achievement Content-Type: text/plain; charset="iso-8859-1" Hi list, A while back, I saw a few notes on the use of the Mann-Whitney test in comparing distinct categories on a likert scale. I am wondering if I can use the same test on 'aggregated likert scale results.' Here is what I am thinking about doing. We have parents' rating of satisfaction with their school on a five-point likert scale. In order to simplify the comparison of school-level satisfaction, the two highest categories were summed and divided by the total number of parents to calculate a measure called 'percent of parents satisfied.' The schools were then grouped into somewhat arbitrary categories: 0-20% satisfied, 20-40% satisfied, 40-60% satisfied, 60-80% satisfied, and 80-100% satisfied. I want to compare the 40-60% satisfied group to the 80-100% satisfied groups. My hypothesis is the higher level of satisfaction should be related to higher student achievement. All grade 4 student took a reading assessment. Each student's score was classified as below, meeting, or exceeding expectation. The student score were aggregated to the school-level by creating a measure of student achievement 'percentage of students meeting or exceeding' (an ordinal scale). So my questions are Can I use a Mann-Whitney test to compare school-level achievement (pct meeting or exceeding) by school-level groups of parents (those with a moderate percentage of satisfied parents and those with a high percentage of satisfied parents)? Does all the aggregation to school level and manipulation into somewhat arbitrary groups invalidate the Mann-Whitney test? Does the variability of school population make all this work invalid? (Both in the satisfaction measure and in the student achievement test, the populations in a school may vary from 1 to 80 respondents and by aggregating, I'm flattening the internal variability.) Thanks for your collected wisdom on this question and all the others I read on the listserv. ------------------------------------------------------------ Pat McCrea (pat.mccrea@gems7.gov.bc.ca) Data Analysis and Reporting, Ministry of Education, PO Box 9143 617 Government St, Victoria BC V8W 9H1 (250) 356-2440 fax (250) 356-0407

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