Module 5 Flashcards
What does it mean to have a simple random sample?
Each possible sample of size n has the same probability of being selected.
What is sampling with replacement?
Element gets put back into population after being selected, and could get selected again.
How do we sample from an infinite population?
- each element must come from the same point in time (same population)
- each element must be selected independently
What’s the central limit theorem?
If the population of xbars is 30 or more, it will approach a normal distribution.
If you increase sample size, what happens?
- probability of pbar being close to p increases
- confidence interval narrows
What are the two categories of sampling methods?
Probability and non-probability sampling
What are the methods of probability sampling
Stratified random sampling
Cluster sampling
Systematic sampling
What are the methods of nonprobability sampling?
Convenience sampling
Judgement sampling
What does probability sampling mean?
Elements have a known probability of being sampled.
What is stratified random sampling?
Elements are grouped into stratum, and then each strata is sampled.
Can yield same results as simple random sampling but with smaller sample size.
What is cluster sampling?
- elements are grouped into exclusive clusters, each with variety representative of population
- random samples of whole clusters taken
- cost effective; can take many samples in just a few locations
What is systematic sampling?
- every nth element is sampled.
What does nonprobability sampling mean?
Elements have an unknown probability of being sampled.
What is convenience sampling?
- volunteer panels, wildlife captures, food inspection
- can’t statistically prove that it’s representative
What is judgement sampling?
Elements are selected because someone knowledgeable feels they are representative.
Very subject to bias.
