A researcher wants to attain a random sample of young drivers who have received DUIs within the last year. Using the PREP system, he asks all first year students at WLU who have received a DUI to volunteer for the study. Thirty-five students actually admit to having received DUIs. He assigns a number to each of these students and chooses 15 participants using a table of random numbers.
Indicate which of the following sampling techniques are examples of random sampling. For those that are not examples of random sampling, explain why.
What do you think?
I think so, but once again.. the wording is confusing me..
Didn't the students select themselves?
well.. 35 students showed up.. but fifteen were only chosen.. which would then be a random sample? right..?
Only 35 admitted to having a DUI. It's likely that many more had DUI's but didn't admit it.
Your sample is skewed.
To obtain a random sample of young drivers who have received DUIs within the last year, the researcher followed the following steps using the PREP system:
1. Define the Population: The researcher narrowed down the target population to first-year students at WLU who have received DUIs within the last year.
2. Randomly Selecting Volunteers: The researcher asked all the first-year students who fit the criteria (those who have received DUIs) to volunteer for the study. The researcher did not force or persuade anyone to participate.
3. Numbering the Volunteers: After the students admitted to having received DUIs, the researcher assigned a unique number to each of the 35 students who volunteered.
4. Choosing Participants: To obtain a smaller, representative sample from the total number of volunteers, the researcher decided to randomly select 15 participants. A table of random numbers helps in this process.
Here's how the researcher used the table of random numbers:
a. The researcher assigned each volunteer a number from 01 to 35, corresponding to their position in the list of volunteers.
b. The researcher then consulted the table of random numbers, which contains a list of random digits from 0 to 9.
c. Starting at any random point in the table (e.g., the first page and first row), the researcher read the digits in pairs or groups of three (depending on the required number range) to ensure statistically random selection.
d. For each random digit, the researcher selected the corresponding numbered volunteer from the list, counting down the list until reaching that number.
e. This process was repeated until 15 participants were chosen. The researcher verified that no duplicates were selected.
By following these steps, the researcher obtained a random sample of 15 young drivers who have received DUIs within the last year from the pool of 35 volunteers at WLU.