Table 6.
MMDs by decade, industry, operation and fluid type
| Classification | No. of measurements | MMD (μm) | SD (μm) | P-valuea | |
| Decade | 1990s | 315 | 5.6 | 0.9 | NS |
| 2000s | 260 | 5.4 | 1.2 | ||
| Industry type | Auto | 315 | 5.6 | 0.9 | NS |
| Small-jobs | 260 | 5.4 | 1.2 | ||
| Operation type | Grinding | 117 | 6.1 | 1.0 | 0.078 |
| Machiningb | 458 | 5.3 | 1.0 | ||
| Fluid type | Straight | 237 | 5.5 | 1.2 | NS |
| Soluble | 206 | 5.7 | 0.7 | ||
| Synthetic | 81 | 5.8 | 1.2 | ||
| Semisynthetic | 51 | 4.2 | 0.9 | ||
| Straight | Grinding | 16 | 6.5 | 2.5 | NS |
| Machiningb | 221 | 5.4 | 1.1 | ||
| Soluble | Grinding | 57 | 6.6 | 0.5 | NS |
| Machiningb | 149 | 5.3 | 0.3 | ||
| Synthetic | Grinding | 30 | 5.4 | 0.4 | NS |
| Machiningb | 51 | 6.0 | 1.4 | ||
| Semisynthetic | Grinding | 14 | 5.1 | 0.9 | 0.026 |
| Machiningb | 37 | 3.8 | 0.6 | ||
| Total | 575 | 5.5 | 1.1 | ||
NS = not statistically significant.
a
Includes milling, drilling, hobbing, tapping, broaching, turning and stamping.
b
P-value, ANOVA (dependent variable = MMDs).