Question

For the following reports about statistical studies, identify the following items (if possible). If you can't tell, then say so-this often happens when we read about a survey. a) The population b) The population parameter of interest c) The sampling frame d) The sample e) The sampling method, including whether or not randomization was employed f) Any potential sources of bias you can detect and any problems you see in generalizing to the population of interest Researchers waited outside a bar they had randomly selected from a list of such establishments. They stopped every 10 th person who came out of the bar and asked whether he or she thought drinking and driving was a serious problem.

Short answer

Population: Bar-goers; Parameter: Proportion believing drinking and driving is serious; Sampling method: Systematic with initial randomization.

Step-by-step solution

Identify the Population

The population consists of all people who visit bars, as the study is interested in the opinions of bar-goers on the issue of drinking and driving.

Determine the Population Parameter

The parameter of interest is the proportion of bar patrons who believe that drinking and driving is a serious problem.

Recognize the Sampling Frame

The sampling frame is the list of all bars from which the bar to conduct the survey was randomly selected.

Identify the Sample

The sample consists of every 10th person exiting the randomly selected bar who was asked the survey question.

Identify the Sampling Method

The researchers used a systematic sampling method, with randomization employed on the selection of the bar from a list.

Analyze Sources of Bias

Potential sources of bias include the limitation to one randomly selected bar, which might not represent all bars, and the possibility that those willing to respond might not fully represent the opinions of typical bar-goers. This sampling method could lead to under-representation of certain demographics who may avoid responding in public or at night.

Key concepts

Population Parameter

The population parameter is a key concept in survey sampling. It refers to the specific measurement or value of interest that researchers aim to evaluate in a population. In the given study, the population parameter is the proportion of bar-goers who perceive drinking and driving as a serious issue. This parameter helps researchers understand the extent to which bar patrons are concerned about this public safety issue.
It's important to clarify that the population parameter is a theoretical value that gives insight into the whole population, although it is derived from a sample. It is vital for drawing meaningful conclusions and making informed decisions based on the collected data. The goal of sampling is to estimate this parameter as accurately as possible from the data.

Sampling Method

Choosing an appropriate sampling method is crucial in survey research to ensure that the findings are representative of the entire population. In this study, the researchers employed a systematic sampling method. This approach involves selecting every 10th person leaving the bar as part of their sample. This method is systematic because it uses a fixed interval to choose participants.
Randomization is another critical aspect here. By randomly selecting a bar from a list of bars, the researchers added a layer of randomness to their sampling process. Randomization is essential as it reduces selection bias, ensuring that the sample reflects the diversity of the population.

• This sampling method is easy to implement and can be quite effective if the population list is a good representation of the overall population.
• However, systematic sampling requires careful consideration of the interval chosen and the order of the list, to avoid patterns that could skew results.

Systematic Sampling

Systematic sampling is a method that simplifies the process of selecting a sample from a larger population by using a fixed, periodic interval. In the exercise at hand, the researchers stopped every 10th person exiting the bar. Such sampling is often used because it is straightforward and tends to be less time-consuming than other methods.
One advantage of systematic sampling is its simplicity and ease of implementation. It eliminates the need for a random number list or other complicated selection processes, making it accessible even for those new to research methods. Additionally, it ensures that the sample is spread evenly across the population, preventing clustering of responses.

• It is crucial to ensure the initial selection point is random to provide each individual an equal probability of selection, except for the systematic position chosen.
• In practice, care must be taken to ensure the population list is not ordered in a way that could introduce unintended patterns affecting the sample.

Bias in Surveys

Survey bias is a common issue that can affect the accuracy and reliability of study results. Bias occurs when certain groups within the population are over- or under-represented in the sample, potentially skewing the findings. In the study discussed, two main types of bias can be identified:

• **Selection Bias:** Since the survey was conducted at a single randomly selected bar, the results may not accurately reflect the views of all bar-goers across different establishments. The atmosphere, clientele, or location of the selected bar may result in opinions that are not representative of the broader population.
• **Response Bias:** This bias can occur if those who choose to respond are more or less likely to perceive drinking and driving as a serious issue. Factors such as being approached at night or in a public setting could influence who chooses to participate.

Understanding and minimizing bias is vital to ensure trustworthy results. Researchers must be diligent in designing surveys that adequately represent the population to draw valid and reliable conclusions.