Question 1: Bias in sampling occurs when certain members of a population are more likely to be selected than others, leading to unrepresentative data. The bias can be caused by various factors such as sampling method or question framing. Understanding and identifying bias is crucial to ensure fair and accurate results.

Answer: Bias occurs when some members are more likely to be selected, causing unrepresentative data.

Question 1: A survey about student preferences is conducted by asking students in the school corridor. Why might this method introduce bias?

Answer: Because only students in the corridor are sampled, not all students, leading to bias.

Question 2: Calculate the bias introduced if a survey on exam stress is only conducted among students attending a revision session, which is attended mainly by anxious students.

Answer: Bias is high because only anxious students are sampled, not representative of all students.

Question 3: A health survey samples only people visiting a particular clinic. How could this introduce bias?

Answer: Because only clinic visitors are sampled, it may not represent the whole population's health status.

Question 4: Construct a sampling plan that minimizes bias when surveying opinions on a new school rule.

Answer: Random sampling of all students or a stratified sample across classes.

Question 1: Explain why online surveys might be biased compared to face-to-face surveys.

Answer: Online surveys may bias towards those with internet access and familiarity, excluding others.

Question 2: A researcher only surveys customers who respond to a follow-up email. What kind of bias might this introduce?

Answer: Response bias, as only those motivated to respond are included.

Question 3: Calculate the percentage bias if a sample of 80 students is taken from a population of 200 students, but only 50 respond, and the responders are mostly from one class.

Answer: Bias is significant because responders are not representative; percentage bias depends on the bias in responses.

Question 4: Identify a potential bias in collecting data on dietary habits by asking only members of a gym.

Answer: Sample is biased towards active or health-conscious individuals, not representative of all.

Question 1: A political poll surveys only supporters of a particular party. How can this introduce bias, and what method would reduce it?

Answer: It leads to bias by overestimating support. Using random sampling across all voters reduces bias.

Question 2: Design a multi-stage sampling method that minimizes bias in a national survey.

Answer: Use stratified sampling by region, then random sampling within each stratum.

Question 1: A student claims that sampling only from social media gives a completely unbiased sample of teenagers. Is this correct? Explain.

Answer: No, because social media users are not representative of all teenagers, introducing bias.

Question 2: A survey reports 70% support for a new policy, based only on responses from urban residents. What mistake has been made?

Answer: Sampling bias due to only urban residents being surveyed.