Another variant of PBL is anchored instruction, exemplified by the Adventures of Jasper Woodbury used in middle school mathematics(Cognition and Technology Group at Vanderbilt(CTGVJ, 1992). In a large-scale implementation study comparing students using the Jasper PBL instruction with matched comparison students across 16 school districts in 11 states, PBL had positive outcomes on standardized tests. On researcher-developed measures, the results showed no differences between PBL and traditional math instruction on single-step word problems but significant positive effects on solving multistep word problems and on other aspects of problem solving such as planning and problem comprehension for the PBL group.