0 a covered opening in a road that a worker can enter in order to reach underground pipes, wires, or drains that need to be examined or repaired -- （地下管道或下水道供人出入檢修的）人孔，檢修孔，檢查井
a manhole cover 檢查井井蓋
The different shadings show the number of manholes in the square.
The number of manholes baited varies from year to year.
The different shadings show the density of rat activity (expressed as number of bait takes per 100 manholes).
The number of statistically significant results found means that the null hypothesis that rodents are evenly distributed amongst the manholes must, therefore, be firmly rejected.
Expected value is total number of hits divided by number of manholes r100 (true alpha=0.0132).
We, therefore, restrict ourselves to saying that there tend to be more hotspots in areas of higher manhole density.
It was important to determine how often annual baiting recorded their presence or activity at each manhole.
Within the tests, the null hypothesis was that rats would be equally likely to be found in each manhole within the system.
