At the Extramural Nexus blog, NIH Office of Extramural Research Director Sally Rockey simplifies the concepts of "paylines, percentiles, and success rates" for grant applicants. Rockey says that "as budgets flatten and tighten," the blogosphere is buzzing with PIs wondering how NIH can "have a success rate of 20 percent but a payline at the seventh percentile?" she says. In her post, Rockey breaks down the terminology and crunches the numbers for percentile rank, paylines, and success rates, providing links to NIH references along the way. In the end, she says, "there are several real-life reasons why paylines — the ones that use percentiles — can be either higher or lower than success rates." For example, Rockey says that NIH still factors applications that are not "percentiled" into its success rate calculations and that success rate of a given year "is a reflection of the funded applications and can include applications reviewed in the previous fiscal year, whereas the payline encompasses only applications reviewed in that fiscal year." With all of these factors, and others, compounding the calculations, it can be difficult for a grant applicant to estimate his or her chances of being funded. To that end, Rockey says that a PI's "best advisor on this issue" is the program official.
Elsewhere at the Extramural Nexus, NIH points applicants to the National Institute of Allergy and Infectious Diseases' Web site, where the agency has posted four funded R01 applications for users' reference.