To expand upon what John has already said, the Part B examination utilizes a "made-up" specification containing various forms, preheat tables, base metal/filler metal combinations, criteria for bend testing, radiography, visual inspection, etc. The plastic sample welds are evaluated based on the requirements of the Part B Specification.
The Part B Specification takes a little from AWS, a little from ASME, and a little from "Lord" knows where, mixes it all up and tosses it at you. You are expected to forget everything you do in the "real world" and use the Part B Specification as it is written. That is easier for some people than it is for other.
There are some calculations involved as well. The calculations are rather simple. They include calculating ultimate tensile strength and elongation. You are expected to use a micrometer and a dial caliper to measure the size of test samples and calculate the cross sectional areas. There may be some comnversions involving converting SI units to customary units and vice versa.
I hope that helps.
Best regards - Al