Hoofdstuk 12: sampling Flashcards
1
Q
Explain the sampling plan
A
- Target pop.: generalize to
- Accesible pop: who can we reach ?
- Sampling frame: through what medium can we reach ?
- Sample: Wo participates ?
2
Q
Eligibility criteria ?
A
Inclusion and exclusion (+costs, practical constraints,…)
3
Q
Sampling bias ?
A
=systematic over or underepresentation of population segment
more homogenity, less bias
4
Q
Explain non-probability sampling (4)
A
=non random sampling
- Convenience: easy to reach pop
- Quota:based on identified strata and size of each group –> proportion is goal –> lowers sampling bias
- Consecutive: all people accesible on specific location over period of time
- Purposive: almost never representative
5
Q
Explain probability sampling (4)
A
=each element has equal chance of being selected
- Simple random: random selection from list
- Stratified random: divide in strata and sample at random
- Multistage cluster: select groups instead of individuals (eg: 10 classes each 20 people-> N=10), is less accurate
- Systematic: every k’th from list = simple random but more convenient
6
Q
sum up some sample size basics
A
- power analysis
- large sample = more representative
- large non-probability sample > small non-prob sample
7
Q
What factors affect sample size
A
- Effect size (expected relationship between var.)
- stong relation –> small sample is okay (analog for weak relation) - Homogenity: more = smaller sample
- Cooperation and attrition: percentage of people likely to cooperate and loss over time
- Sub group analysis: samples must be large enough to support analysis within subgroups
