A) To establish a sampling plan, follow these 5 steps:
1) Identify the sample population: which customers will you reach out to?
Those who purchased a new car during a specific year.
2) Determine the population size: how many customers will you contact?
From the 30,000 car buyers, select 1,000 customers to contact.
3) Select contact method: what is your means of contacting customers?
Since you have a list with names and addresses, mailing questionnaires is feasible.
4) Define the sampling frame: what is the timeline or deadline for contacting customers?
Send out questionnaires and allow two months for responses.
5) Decide on the analysis approach: is your research qualitative or quantitative?
You aim for quantitative research, so you will use probabilistic sampling.
B) The 32.5% probability relates only to those customers who experienced mechanical issues, specifically power door lock problems, and does not account for those without any problems or those reporting issues after the first 5,000 miles.
C) To estimate the probability of power door lock problems among all customers within the first 5,000 miles, consider the entire sample:
P = 13 / 1000 = 0.013
Therefore,
N = 0.013 × 30,000 = 390
Thus, the estimated number of new cars that had power door lock issues within 5,000 miles is 390.
