Question 45·Hard·Command of Evidence
In high-precision 3D printing, a small shift in the position of a printer’s nozzle can increase dimensional error in printed parts. Some printers include a calibration routine designed to correct such shifts; if the routine is effective, the printer’s error after calibration should return to (or improve on) its baseline level.
In a test of a new calibration routine, engineers measured the average absolute dimensional error (in millimeters) for three printers under three conditions: baseline, after an induced nozzle shift, and after running the calibration routine. The results are shown in the graph.
The engineers concluded that the calibration routine may not reliably restore printers to their baseline accuracy, citing as evidence the fact that the printers in the study _____
Which choice most effectively uses data from the graph to complete the statement?
For command-of-evidence completions tied to a graph, restate the claim in the sentence (here, lack of reliable return to baseline). Then check the exact comparison the claim requires (baseline vs. corrected for each printer) and choose the option that matches the overall pattern across all cases, not just a single printer or a different comparison (like shifted vs. corrected).
Hints
Focus on the word “reliably”
If something is reliable, it works the same way each time. Look for whether the calibration result is consistent across all three printers.
Compare two bars for each printer
For each printer, compare the baseline bar to the corrected bar. Are they equal, or is corrected still higher?
Check how many printers meet the goal
Count how many printers return to baseline after calibration. The right choice should reflect that count accurately.
Step-by-step Explanation
Identify what the conclusion requires
The engineers claim the routine may not be reliable, so the supporting evidence should show that the routine does not bring printers back to baseline accuracy in a consistent way.
Compare baseline to post-calibration for each printer
From the graph:
- Printer A: baseline mm, corrected mm (at or better than baseline)
- Printer B: baseline mm, corrected mm (worse than baseline)
- Printer C: baseline mm, corrected mm (worse than baseline)
Match the evidence to the blank
Because calibration helps compared with the shifted condition but still leaves two printers above baseline, the best completion is “reduced error after the induced shift but still left two printers with error above baseline”.