Cluster sampling refers to a type of sampling method . With cluster sampling, the researcher divides the population into separate groups, called clusters. Then, a simple random sample of clusters is selected from the population. The researcher conducts his analysis on data from the sampled clusters.
If you are running around an actual football field (100 yds x 50 yds) a mile would be 5.9 laps (1 mi = 1760 yds/300 = 5.86667). A standard racetrack around a football field should be 440 yds, so 4 laps should be a mile there (1760/440 = 4).
It's rough, tough, and most of the time, extremely violent. The rectangular field is 160 feet (48.5 m) wide and 360 feet (109.1 m) in length (53.3 yards, 120 yards respectively), including the two 10 yard (9.2 m) end zones. If you know the rules of the game, then you should know how hard it is to gain just one yard.