A half-dozen UC Davis graduate programs rank among the best of the nation in a comprehensive survey of doctorate programs released today (Sept. 28) by the National Research Council. It is the first survey of its kind since 1995.

Among the best UC Davis performers were the graduate programs in Spanish, entomology, agricultural and resource economics, plant biology, ecology, and nutritional biology, all of which fell in the top 5 percent among similar programs nationally on at least one of two overall measures. About one-third of the UC Davis programs fell in the top 25 percent in their respective fields.

"The strong overall performance of so many UC Davis graduate programs reflects the talent and energy of the faculty and the interdisciplinary environment on campus," said Jeffery Gibeling, dean of graduate studies. The results quantitatively validate what we already know about some of our best programs, he added.

"At UC Davis and, I expect, at other Ph.D.-granting universities, we will be carefully working through these data, making comparisons between our programs and those at other institutions, and looking for ways that we can improve," Gibeling said. "It is likely that we will construct our own rankings based on the qualities we believe to be most important."

Gibeling cautioned against making simple head-to-head comparisons of rankings. The NRC describes the rankings as "illustrative" of the ways the data can be used and does not endorse their use to make absolute comparisons. Different UC Davis programs do well in different subcategories, he noted.

Data for the survey were collected in 2006 and reflect the 10 years before that. Changes since 2006, such as changes in curriculum or faculty turnover or growth, are not captured.

While the data in the survey are in some ways dated, it is the most comprehensive and detailed survey of its kind, and can provide useful information for future policy discussions on strengthening graduate education at UC Davis, Gibeling said.

Fifty-one UC Davis programs were included in the survey. Eligible programs had to have graduated at least five Ph.D.s in the five years prior to 2005-06. Programs were slotted into specific subject fields determined in advance by the NRC. In some cases, multiple UC Davis programs fit in the same subject field. One important change since the 1995 NRC assessment is the inclusion of agricultural fields, areas in which UC Davis has longstanding strengths.

The report's methodology is complex. The committee assigned each program a range of ranks on five different scales: two overall scales, "overall-S" and "overall-R," and three subcategories, "research activity," "student support and outcomes," and "diversity of the academic environment."

The results for each measure are expressed as a range of rankings reflecting the variability and uncertainty inherent in such assessments. For example, the UC Davis graduate program in entomology was ranked from 1 to 7 on the overall-S scale, 2 to 10 on overall-R, 2 to 13 for research activity, 3 to 15 for student support and outcomes, and 3 to 12 on diversity.

Those rankings might be skewed in fields with few programs in the country: For example, it is easier to be in the top 10 programs if only 15 such programs are offered nationwide than if there are 150. So the rank ranges can also be expressed as percentile ranges.

To calculate the rankings, the NRC collected data on 20 key variables, grouped under the three subcategory headings.

The NRC's statisticians weighted these variables in two different ways. In the first method, they surveyed university faculty across the country and asked them what factors, such as publications by faculty or time to degree, were most important in the quality of a graduate program. These "survey" weights were used to calculate the "overall-S" score.

In the second method, they asked small groups of professors to rank a subset of programs in a particular field. Then they used regression analysis to work out which variables best predict the program rankings reported by the faculty. This set of weights was used to calculate the "overall-R" score.

The NRC's statisticians analyzed the data 500 times and discarded the top and bottom 5 percent of results to arrive at a range of values, said Division of Graduate Studies analyst Helen Frasier. Statistically, there is a 90 percent probability that the true rank of the program falls into that range.

The overall-S and overall-R scores give divergent results in some cases. The size of a program, for example, has a bigger effect on the overall-R score, Frasier said.

For example, Spanish was ranked 1 to 6 (98th to 90th percentile) on the overall-S scale, but 13 to 42 (78th to 30th percentile) on the overall-R scale. Ecology was ranked from 5 to 28 (95th to 70th percentile) on the overall-S scale, but from 1 to 4 (99th to 96th percentile) on the overall-R scale.

Rankings in the three subcategories highlight different areas of strength, Gibeling said. For example, across the country, it is common for programs that ranked high on research activity to rank lower on diversity.

Nationally, the NRC noted that more students and faculty are participating in doctoral education than in 1995. In particular, the council observed that doctoral education has benefited from dramatic increases in enrollments of international students, minorities and women. These changes reflect the continuing value of U.S. doctoral education and the ability of graduate programs to reach U.S. citizens who have been historically underrepresented in Ph.D. programs, the report said.