Determine whether a census is practical in the situation described?

For the first example, the local high school football team probably isn't that huge. Even if the school didn't believe in tryouts and allowed everyone who was interested to be on the team, it is reasonable to think you could grab a notebook and a scale, weigh, and record the weight of everyone on the team. You then need to average them, but the math can be done with a standard calculator. Using a census for this scenario and reaching every team member seems plausible.

For the second example, determining the average cholesterol level of all biology instructors in the US is less feasible with a census. If you have unlimited time and money, of course anything is possible, but doing this in-person would be difficult. You'd need to travel to Alaska and Hawaii (not to mention the 48 other states).

Measuring someone's cholesterol isn't as simple as having someone step on a scale. You need to take their blood and send it to a lab.

Even if you mailed requests to every biology instructor in the US and asked them to self-report their levels (in this case you're relying on people to be honest), you would need to decide how recent you want the measurement to be (if someone had their cholesterol level measured last year, is this acceptable data?) and many people likely won't know their levels. You are then relying on people to see their doctors, have their blood drawn, and then report back. Without compensation of some sort, this is a relatively time-consuming request for most people.

The National Science Teachers Association estimates that there are about two million science teachers in the US. Now of course this doesn't mean they all teach biology, but even if 1/4 do, this is a lot of people. If we consider college instructors, the number increases.

For these reasons, a census measuring every biology instructor's cholesterol is not practical. Using a sample of the population and testing their cholesterol is probably a better idea.

To determine whether a census is practical in a given situation, several factors need to be considered, including the size of the population, available resources, timeframe, and the level of accuracy required. If the population is relatively small, resources are sufficient, and there is ample time to conduct the census, it may be practical. However, if the population is very large, resources are limited, or time is constrained, alternative sampling methods such as random sampling or stratified sampling may be more practical to obtain accurate data without the extensive resources required for a full census.