Purpose of sampling and target population; Bias and reliability; Simple random, stratified and systematic samples; Sample size effects
Example 1
A population has 200 people, of whom 80 are in group A. A proportional stratified sample has 40 people. How many should be from A?
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Answer: 16
- Group A is 40% of the population; allocate 40% of the sample.
Example 2
Which method is most likely to reduce selection bias?
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Answer: Randomly select from a complete population list
- Random selection from a suitable frame gives members a known selection opportunity.
Example 3
A random sample has 80 selected people but only 60 respond. Find the response rate as a percentage.
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Answer: 75
- Response rate = respondents/selected ×100=2015×100=75%.