Correct Response: C. The pH meters may not be equally accurate. This can introduce errors in measurement associated with which meter is used by the students. It would be preferable for the students to use the same pH meter, or at least calibrate all four of the existing meters to some standard. The rounding errors (A) are essentially random, not systematic, in nature. Students should use the same protocol when making the measurements (B), which should reduce the associated error in measurement. Sampling at the same time every day should minimize daily fluctuations in the data (D).
