Introduction to sample surveys

Why sample?

• cheaper than census
• quicker
• better control of response quality

Basic procedure:

1. decide on objectives
2. choose sampling units
3. choose mode of sampling
4. design measuring instrument
5. pilot
6. choose sampling design
7. choose sample size
8. select units
9. train interviewers
10. enter and check data
11. anaylse

Two types of surveys:

• descriptive: estimate some characteristic of population
• analytic: examine some relationship between variables

Sampling distributions

Why use random sampling?

• removes subjective bias
• lets us assess accuracy of estimates
• results will be more acceptable to wider audience
• guarantees accurary proportional to sample size

Have chosen to use random sampling, but still have a lot of flexibility in choice of randomisation scheme, and some flexibility in choice of estimator. Can use MSE $= Var(\bar{y}) + bias^2$ to compare estimators and randomisation schemes.