What is the shift tolerance for moisture counts?

• A. A shift of 5% or less
• B. A shift of 2% or less
• C. A shift of 1% or less
• D. A shift of 3% or less

Answer: (B)

Moisture counts can vary from test to test due to factors like sample differences and environmental changes, so a shift tolerance sets how much those readings are allowed to wander while still being acceptable. Two percent or less is used because it strikes a balance: it accounts for natural moisture variability but keeps the moisture-density relationship stable enough for consistent compaction results. A looser tolerance would let too much variation creep in, undermining quality control, while a tighter one would be unrealistic in field conditions. So, two percent or less.