Topic 4.12: Linear Regression Questions

Which sampling method gives every possible group of the chosen size an equal chance of being selected?

A company has 900 employees: 540 in production and 360 in offices. A stratified sample of 30 is taken. Find how many office employees should be sampled.

Picking every 10th house along a street, starting from a randomly chosen one of the first 10, is:

A population of 2000 is split into 1200 town and 800 rural residents. A stratified sample of 100 is taken. How many rural residents are sampled?

An exam-revision app surveys only its premium users about how helpful the app is, then claims the result reflects all users. The main problem is that the conclusion is:

A researcher stands at a supermarket exit on a Tuesday morning and interviews the first 50 shoppers who agree to talk. State the sampling method and explain one reason the sample may be biased.

Explain the difference between a measuring instrument being reliable and being valid. Give an example of an instrument that is reliable but not valid.

A school of 1500 students has year groups of sizes 400, 380, 360, 200 and 160. A stratified sample of 75 is taken. Find the number sampled from the largest year group, and comment on why stratified sampling is preferable to convenience sampling here.

A watch runs at a steady but slightly wrong speed, always reading 4 minutes fast. The watch is:

To estimate the mean weight of apples from an orchard of 2000 trees, an inspector picks the 40 trees nearest the gate and weighs one apple from each. Identify the sampling method, state whether the resulting mean is likely to be a valid estimate, and suggest a better method.

A market researcher is told to interview 60 people made up of 30 men and 30 women, choosing whoever she likes to fill each total. Separately, a colleague randomly selects 30 men and 30 women from a full customer list. Name each method and state which is more likely to give an unbiased sample.