Question

A researcher wants to determine the proportion of vehicles in the Denver area that are driven with cracked windshields. The research team goes to the ten Denver International Airport (DIA) parking lots (Valet West, Valet East, Short Term West, Short Term East, Garage West, Garage East, Economy Lot West, Economy Lot East, Pikes Peak Shuttle Lot, Mt. Elbert Shuttle Lot) to record information. The parking lots do not have the same number of total spaces. Five random rows are selected at each parking lot. The number of vehicles in the row and the number with a crack in the windshield are recorded.

What is the population being studied?
What is the sampling technique?
Discuss advantages and disadvantages of this plan.
Explain each question in one to two sentences.

Answer 1

1.) The population being studied are the individuals who own vehicles in the Denver area.

2.) The sampling technique used here is stratified random sampling. The homogenous stratas are the 10 parking lots selected from which sample of 5 rows are selected using simple random sampling.

3.) Advantage - By using stratified random sampling, we can maintain greater precision of the estimate obtained.

Disadvantage - The units within stratas should be homogenous, but stratas themselves should be as heterogenous as possible.

Considering the fact that all the lots selected are International airport parking lots, there may not be vast heterogeneity in the lots selected to conclude about the entire Denver area for cracked windshields of vehicles driven.