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Suppose you attend a school that offers both traditional courses and online courses. You want to know the average age of all the students. You walk around campus asking those students that you meet how old they are. Would this result in an unbiased sample?

Short Answer

Expert verified
No, this would not result in an unbiased sample as it disregards the online students who might not be present on campus.

Step by step solution

01

Define Sampling Bias

Sampling bias occurs when the sample obtained does not represent the entire population accurately. It means that some members of the population have a lower or higher chance of being included in the sample than others.
02

Analyze the Sampling Method

In this case, the method used to gather the survey is by asking age from the students encountered on campus.
03

Identify Potential Bias

Students who attend classes online and do not come to campus are ignored this way. They are not considered in the sampling process. Consequently, they are less likely to be included in the sample, creating a potential bias.
04

Conclusion about the Sample

Due to the possibility of a higher average age among online students (as they could possibly be working while studying), or otherwise, which won't be represented in this sample, the sample is likely to be biased. Thus, the sample does not accurately represent the average age of all students at the school.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Unbiased Sample
An unbiased sample is one that accurately reflects the entire population you aim to study, without any form of prejudice or skew. It ensures that every individual in the population has an equal opportunity to be chosen. This is essential for reliable data, which serves as the foundation for well-informed conclusions and decisions.

To attain an unbiased sample, you must carefully consider how individuals are selected from the population. Bias often enters unintentionally, skewing results. For instance, if you gather information only from students present on campus, you could be inadvertently excluding online students from your sample.

A truly unbiased sample aims to account for all groups within the population, ensuring comprehensive representation. Random sampling methods, where every individual has an equal chance of selection, often aid in achieving this. Consistent vigilance to minimize bias will lead to more accurate results and a clearer understanding of the population's characteristics.
Sampling Method
The sampling method refers to the strategy used to select individuals from the population to be included in your study. The right method can help ensure your sample mirrors the larger population as closely as possible.

In the context of the exercise, the method was simply asking students encountered on campus. While convenient, this approach does not guarantee a representative sample of the total student body, including both online and on-campus students.

Choosing a method involves considering the specifics of your population and the information you're after.
  • Random Sampling: Every member of the population has an equal chance of being selected. This is ideal for reducing bias.
  • Stratified Sampling: Divides the population into subgroups (or strata) and then samples from each subgroup, ensuring all key segments are represented.
  • Systematic Sampling: Involves selecting every nth individual from a list or sequence, providing simplicity but not necessarily eliminating bias.
Each method has its trade-offs. The goal is always to maximize representativeness while minimizing bias.
Population Representation
Population representation is the extent to which a sample reflects the characteristics and diversity of the larger group it is meant to represent. A well-represented sample ensures that the traits, opinions, and variables of the entire population are accurately echoed in the study results.

In the exercise scenario, seeking information only from students on campus overlooks those who might have unique characteristics and demographics, such as online students. This neglect leads to a skewed perception of the average student age.

To achieve proper population representation, the sample should include individuals from all segments of the community. Consideration of demographic factors, geographic distribution, and other categorical variables is crucial. Methods such as stratified sampling help ensure that all key groups are represented according to their prevalence in the total population. Including diverse perspectives provides a fuller, more truthful image of the population as a whole.

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Most popular questions from this chapter

The Gallup poll reported that \(45 \%\) of Americans have tried marijuana. This was based on a survey of 1021 Americans and had a margin of error of plus or minus 5 percentage points with a \(95 \%\) level of confidence. a. State the survey results in confidence interval form and interpret the interval. b. If the Gallup Poll was to conduct 100 such surveys of 1021 Americans, how many of them would result in confidence intervals that did not include the true population proportion? c. Suppose a student wrote this interpretation of the interval: "We are \(95 \%\) confident that the percentage of Americans who have tried marijuana is between \(40 \%\) and \(50 \% .\) " What, if anything, is incorrect in this interpretation?

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