Table of contents
- 1. Intro to Stats and Collecting Data55m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically1h 45m
- 4. Probability2h 16m
- 5. Binomial Distribution & Discrete Random Variables2h 33m
- 6. Normal Distribution and Continuous Random Variables1h 38m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
1. Intro to Stats and Collecting Data
Intro to Stats
Problem 1.1.1
Textbook Question
Computer Virus In an AOL survey of Internet users, this question was posted online: “Have you ever been hit by a computer virus?” Among the 170,063 responses, 63% answered “yes.” What term is used to describe this type of survey in which the people surveyed consist of those who chose to respond? What is wrong with this type of sampling method?

1
Identify the type of survey: This survey is an example of a 'voluntary response sample' because it consists of individuals who chose to respond to the survey question.
Understand the nature of voluntary response samples: In voluntary response samples, participants self-select to be part of the survey, which can lead to biased results.
Explain the potential bias: The main issue with voluntary response samples is that they often attract individuals with strong opinions or experiences related to the survey topic, which may not represent the general population.
Discuss the impact of bias: Due to the self-selection bias, the results of the survey may not be generalizable to the entire population of Internet users, as those who have experienced a computer virus might be more inclined to respond.
Consider alternative sampling methods: To obtain more representative results, a random sampling method could be used, where every individual in the population has an equal chance of being selected for the survey.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Voluntary Response Sample
A voluntary response sample is a type of non-probability sampling method where participants self-select to be part of the survey. This often leads to biased results because individuals with strong opinions or interests in the topic are more likely to respond, which may not represent the broader population accurately.
Recommended video:
Sampling Distribution of Sample Proportion
Sampling Bias
Sampling bias occurs when the sample collected is not representative of the population intended to be analyzed. In the context of voluntary response samples, the bias arises because the sample is skewed towards individuals who are more motivated to respond, often leading to overrepresentation of certain viewpoints and underrepresentation of others.
Recommended video:
Sampling Distribution of Sample Proportion
Non-Probability Sampling
Non-probability sampling refers to sampling techniques where not all members of the population have a chance of being selected. This contrasts with probability sampling, where every member has a known, non-zero chance of being chosen. Non-probability methods, like voluntary response sampling, can lead to biased results and limit the generalizability of the findings.
Recommended video:
Sampling Distribution of Sample Proportion
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