A newspaper wants to take a poll about which candidate voters
prefer for President. Identify any bias in the following sampling
method:
The newspaper calls people selected at random from
the local telephone book
The sampling method is biased because it only includes people who have a telephone and are listed in the local telephone book. This excludes people who may not have a phone, have an unlisted number, or use a cell phone instead of a landline. This could lead to a sample that does not accurately represent the entire population of voters.
The bias in the sampling method is that it only includes individuals who have a landline phone and are listed in the local telephone book. This could lead to an underrepresentation of certain demographics, such as younger or more mobile individuals who primarily use cell phones and are not listed in the telephone book. Additionally, it may not include individuals who do not have a phone at all.
The bias in the sampling method of calling people selected at random from the local telephone book is called "selection bias."
The main issue with this sampling method is that it may not accurately represent the entire population of voters. There are several potential sources of bias in this approach:
1. Exclusion of individuals without a telephone: This sampling method would exclude individuals who do not have access to a telephone or who rely on other means of communication. This could potentially skew the results as certain demographics, such as lower-income or older individuals, may be disproportionately affected.
2. Exclusion of unlisted numbers: Many individuals choose to have unlisted phone numbers for privacy reasons. By relying solely on the published telephone book, this sampling method would exclude those unlisted numbers, potentially leading to a biased sample.
3. Limited age groups: People who primarily use mobile phones or other alternative means of communication may not be listed in the local telephone book, especially younger individuals. Consequently, the sample would likely skew towards the older population.
To reduce bias, the newspaper could consider implementing a more representative sampling method, such as using a random digit dialing technique to reach a broader range of individuals, including those without landline telephones. Additionally, they could supplement the telephone survey with other methods such as online surveys or in-person interviews to reach a more diverse set of voters. This would help to ensure that the sample represents the larger population accurately.