At a high school with over 500 students, a counselor wants to estimate the mean number of hours per week that students at the school spend in community service activities. The counselor will survey 20 students in the environmental club at the school. The mean number of hours for the 20 students will be used to estimate the population mean.

In order to take a test,the college board requires a form of identification. these strict rules are in place to keep people from taking other people's test. 

Loss in amenity , biodiversity , which are most difficult to assess

Which of the following is an example of an opposing signal? no examplthates given.   i would say, that traffic lights in a city at major intersections direct the flow of traffic in opposite directions so would be an example.also, stop signs on either side of the same street would be an example. at a train crossing, the light for allowing car traffic in opposite directions or not would be another example.