Assistant Professor Dr. David Nordstokke successfully defends PhD dissertation

March 2, 2009 -- The Division of Applied Psychology, colleagues and graduate students, extend warm congratulations to Dr. David Nordstokke on successfully defending his PhD dissertation.

Nordstokke became an Assistant Professor in September 2008, and has particular interests in statistical modeling, test construction and validation, use of simulation in research and teaching, and foundational issues in measurement and statistics. He has worked with a number of renowned academics including his dissertation supervisor Dr. Bruno Zumbo, an internationally renowned scholar in the area of MERM (Measurement, Evaluation, and Research Methodology) at the University of British Columbia.

“Nordstokke did an outstanding job in defending his dissertation,” Zumbo reported to Associate Dean Vicki Schwean

Nordstokke began his dissertation titled, “Investigating tests for equal variances” in September 2005.

“I really put my nose to the grindstone to get it completed in just over three years,” Nordstokke says.

One of the central messages of his dissertation is that (a) unequal variances may be more prevalent than typically recognized in educational and policy research, and (b) when considering tests of equal variances, one needs to be cautious about what is being referred to as “Levene’s test” because Levene’s test is actually a family of techniques. Depending on which of the Levene tests that are being implemented, and particularly the Levene’s test based on means which is found in widely used software like SPSS, one may be using a statistical technique that is as bad (if not worse) than the F test which the Levene test was intended to replace.

The primary goals of his dissertation are to (a) demonstrate that the current statistical practice of testing for equality of variances in hypothesis testing (as prescribed by textbooks and statistical software programs) is insufficient, (b) introduce a new non-parametric statistical test for homogeneity of variances, and (c) investigate the Type I error rate and power of the non-parametric Levene test with that of the median version of the Levene test. Under all conditions investigated, both tests maintained their nominal Type I error rates.  As population distributions become more skewed, the non-parametric Levene test becomes more powerful than the median version of the Levene test. These results promise to impact applied statistical practice by informing researchers about the relative efficiencies of the two tests.

Nordstokke's dissertation concludes with remarks about the implications of the findings, and the future work that has arisen from the results.

Nordstokke has also provided statistical and methodological consulting for faculty members and graduate students in multiple areas, including Health, Bio-Psychology, Human Development, Educational measurement, Linguistics, and Cross-Cultural measurement. He is also teaching a course in advanced statistical methods.

Outside of academics, Nordstokke particularly enjoys hiking and climbing. You can find him in the education tower in room 334.