Data collected on each observational unit in the sample can be used to approximate characteristics for the entire population. Ex: estimating the proportion of all passengers from each city. Population Sample . . . . . . . . . . . . . . . . . . 2 million = 7,000 Captions A project to understand train passengers' satisfaction with train usage in the five largest cities in Australia will use data collected from surveying passengers. Because of logistics and cost, all adult train passengers from the five cities in Australia cannot be surveyed. A sampling method is used to select the 7,000 passengers to survey. Data collected on each observational unit in the sample can be used to approximate characteristics for the entire population. Ex: estimating the proportion of all passengers from each city.