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Course: Statistics and probability>Unit 6

Lesson 2: Sampling and observational studies

Examples of bias in surveys

Examples of bias in surveys.

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• What are the differences between voluntary response sampling, Response bias, and under coverage?
• Voluntary response bias occurs when there sample is responding to the question without being randomly selected. The sample chooses themselves to partake in the survey. This creates bias because people with strong opinions (often in the same direction) are most likely to respond.

Response bias is a systematic pattern of incorrect responses in a sample survey. These people can be: untruthful-- for several reasons: sensitive question, socially acceptable answer, or telling the interviewer what he or she wants to hear; Ignorant-- People give silly answers just so they won't appear like they know nothing about the subject; lack of memory-- give a wrong answer simply because a subject cannot remember; or timing-- When a survey is taken can have an impact on the answers.

Under coverage occurs when the design of the study does not cover everyone in the population (because they cannot be reached or they are left out); For instance, using a random phone number generator for landlines to get a sample from the population, but not everyone in the population owns landlines anymore, so they get excluded and are left out, or doing a survey when people cannot be reached.

I hope this helps you!
• What are the differences between undercoverage and convenience sampling ?
• Undercoverage is where we haven't sampled enough of the population to make any valid conclusions.

Convenience sampling is where we chose a sample from the population based on how convenient it is to sample them. This introduces a bias and is not representative.
• What is the right way to observe something other than using the voluntary response sampling? I know it's intuitive that voluntary response sampling may skew the result, but are we supposed to force people involuntarily to be our subject of observation? Or maybe we don't force them necessarily, it's just that they don't have a choice to refuse? Well, it's still coercion, isn't it? I still don't get it.
• In research, it's essential to balance the need for representative data with ethical considerations regarding participant autonomy. While voluntary response sampling may lead to biased results due to self-selection, forcing individuals to participate involuntarily is not ethically acceptable. Instead, researchers often opt for probability sampling methods, such as simple random sampling or stratified sampling, where every member of the population has a chance of being selected without coercion. These methods aim to obtain a representative sample while respecting individuals' rights. Alternatively, non-probability sampling methods may be used with caution, acknowledging and addressing potential biases to ensure the integrity of research findings without compromising ethical principles.
• Is voluntary response when those being asked have the option not to respond, or just when the question itself does not have an assigned sample it is asking?

A question on the Practice: Bias in Samples and Surveys exercises read like this, "A mobile phone service provider wants to survey its customers to study privacy concerns and the sharing of their personal information. They call 5,000 randomly selected phone numbers from a database containing the phone number of every customer. If someone selected doesn't answer, they'll attempt calling back up to 2 more times before giving up on reaching that person.

They reach 350 customers with this strategy, and 60% of those reached say they are at least "somewhat concerned" about their personal information being shared without their knowledge or consent.

Which of these is the most concerning potential source of bias in the provider's survey?"

The answer is Nonresponse bias because of how many did not respond, but one of the options was bias from voluntary response. The reason it gives for this not being correct is, "Voluntary response is when a researcher gives an open invitation and people decide to be in the sampler not. the service provider selected a random sample of 5000 customers so they didn't use a voluntary response strategy"

Again, I know it isn't the correct answer, but I thought voluntary response was a correct way of describing the situation. If not then voluntary response seems like a not so accurate label
• this is the best response ever , thanks
• Can you still solve with negative numbers?
• That would be a hypothetical situation, you cant have -200 podcast listeners. That would be called an imaginary number. of course, I'm not an expert.
• a survey of high school students to measure teenage use of illegal drugs will be a biased sample because it does not include home-schooled students or dropouts. A sample is also biased if certain members are underrepresented or overrepresented relative to others in the population.
• Can you still solve with negative numbers?
• Well, not in this case. I don't think there is such a thing as a negative number of people.