Practice Sampling Bias in Statistics
Use these practice problems to test your method after reviewing the concept explanation and worked examples.
Quick Recap
Sampling bias occurs when a sample is collected in a way that systematically makes some members of the population more likely to be included than others, producing results that do not accurately represent the full population and leading to misleading conclusions.
Asking only your friends about favorite music doesn't tell you what the whole school thinks - your friends probably have similar tastes! That's bias. A good sample is like a well-shuffled deck: everyone has an equal chance of being picked.
Showing a random 20 of 50 problems.
Example 1
easyWhere in the polling process does sampling bias originate: in question wording, in how the sample is chosen, or in how data are analyzed?
Example 2
mediumA customer-satisfaction survey gets responses mostly from very angry or very pleased customers. Name this bias and one way to reduce it.
Example 3
hardAn insurance company analyzes only claims that were paid out, then claims its product is reliable. Name the bias and explain why it inflates reliability.
Example 4
challengeTo reduce bias when some groups are hard to reach, a researcher proposes sampling extra heavily from easy-to-reach groups 'to get a bigger sample.' Explain why this worsens bias and propose a better fix.
Example 5
challengeSurvey 1 finds 70% support using random digit dialing of landlines only; Survey 2 finds 55% support using a properly mixed random sample of all phone types. The true value is unknown. Explain why Survey 1's number is likely biased and in which direction you cannot be sure without more info.
Example 6
easyAn interviewer wears a company-branded shirt and asks people whether they like the company. Why might responses be biased?
Example 7
easyA school wants to know whether students prefer longer lunch breaks. They survey students in the cafeteria at lunchtime. Identify the sampling bias.
Example 8
mediumA question reads, 'Don't you think the government should fix the awful traffic problem?' Identify the bias and one way to fix it.
Example 9
easyA teacher surveys only the front-row students about class difficulty and generalizes to the class. Why is this biased?
Example 10
mediumA pollster randomly selects 2,000 phone numbers but 90% don't answer; the 10% who do skew older. Name the bias and explain why random selection didn't prevent it.
Example 11
mediumA website runs an online poll asking 'Should the government raise taxes?' and 90% of respondents say 'No'. Can this result be trusted? Explain what type of bias is present.
Example 12
easyName one design feature of a survey that helps reduce sampling bias.
Example 13
mediumA national poll boasts respondents — but conducted only online. Why can it still be biased relative to 'all adults'?
Example 14
mediumA survey reaches people only via a daytime landline. Working adults are underrepresented. Name the bias and one practical fix.
Example 15
hardTwo studies estimate average daily exercise. Study A randomly samples from a national list and gets a response rate. Study B randomly samples with personal follow-up to a response rate. Which is likelier less biased?
Example 16
easyA poll about a product is sent only to past buyers. Why might satisfaction be overstated?
Example 17
mediumTwo surveys estimate average income. Survey A randomly samples 300 households; Survey B samples 5,000 households but only those listed in a luxury-magazine directory. Which is more trustworthy and why?
Example 18
mediumA study evaluates a tutoring program by averaging the after-grades of students whose parents signed them up. What sampling problem applies?
Example 19
easyA teacher polls only students who got A's about how easy the test was. What bias is this?
Example 20
mediumA poll asks 'Don't you agree that the unfair new tax should be repealed?' Why does the wording create bias, and what type is it?