Frank purchases 18 gallons of gas on monday he uses 1/3 of the amount commuting to and from work he uses an additional 4 gallons running errands how many gallons of gas does frank use for work and errands

Identify all the cases where non-probability sampling is used when attempting to study the characteristics of a large city. studies on every subject in the population divide a population in groups and obtain a sample studies with a limited amount of time demonstrate existing traits in a population studies with the nth person selected