QuantileGradeR - Quantile-Adjusted Restaurant Grading
Implementation of the food safety restaurant grading
system adopted by Public Health - Seattle & King County (see
Ashwood, Z.C., Elias, B., and Ho. D.E. "Improving the
Reliability of Food Safety Disclosure: A Quantile Adjusted
Restaurant Grading System for Seattle-King County" (working
paper)). As reported in the accompanying paper, this package
allows jurisdictions to easily implement refinements that
address common challenges with unadjusted grading systems.
First, in contrast to unadjusted grading, where the most recent
single routine inspection is the primary determinant of a
grade, grading inputs are allowed to be flexible. For instance,
it is straightforward to base the grade on average inspection
scores across multiple inspection cycles. Second, the package
can identify quantile cutoffs by inputting substantively
meaningful regulatory thresholds (e.g., the proportion of
establishments receiving sufficient violation points to warrant
a return visit). Third, the quantile adjustment equalizes the
proportion of establishments in a flexible number of grading
categories (e.g., A/B/C) across areas (e.g., ZIP codes,
inspector areas) to account for inspector differences. Fourth,
the package implements a refined quantile adjustment that
addresses two limitations with the stats::quantile() function
when applied to inspection score datasets with large numbers of
score ties. The quantile adjustment algorithm iterates over
quantiles until, over all restaurants in all areas, grading
proportions are within a tolerance of desired global
proportions. In addition the package allows a modified
definition of "quantile" from "Nearest Rank". Instead of
requiring that at least p[1]% of restaurants receive the top
grade and at least (p[1]+p[2])% of restaurants receive the top
or second best grade for quantiles p, the algorithm searches
for cutoffs so that as close as possible p[1]% of restaurants
receive the top grade, and as close as possible to p[2]% of
restaurants receive the second top grade.
