An environmental researcher plans to investigate the air quality in a city to estimate the average daily exposure of a typical resident to fine particulate matter ($P{M}_{2.5}$). The city consists of three distinct zones: a pedestrianised commercial centre, a busy multi-lane ring road, and quiet suburban residential streets.

The researcher's proposed sampling plan is as follows:

• Generate 8 random grid coordinates across a map of the entire city.
• Take a single $P{M}_{2.5}$ measurement at each coordinate using a portable sensor for a duration of 5 minutes at 11:00 AM on a Sunday.
• Calculate the arithmetic mean of these 8 measurements to represent the typical daily exposure of a city resident.