Chapter 1 Flashcards
What does a population consist of?
All the items we are interested in(not always people)
What is a sample?
A subset of items chosen from a population
What is each individual item in the population that can be sampled known as?
A sampling unit
What is a sampling frame?
Sampling units from a population individually framed or numbered to form a list called a sampling frame
What is the advantage of a census?
Should give a completely accurate result
3 disadvantages of a census?
-time consuming and expensive
-large volumes of data to process
-can not be used when testing involves destruction
3 advantages of a sample?
-less expensive
-less time consuming
-less data to process
3 disadvantages of a sample?
-data may not be accurate-
sample may not be large enough to represent small sub-groups of the population
Simple random sampling..
Allocate between 1 and N to each pupil
-Siena random number generator to select x different numbers, pupils corresponding to the numbers get selected
3 advantages of simple random sampling?
-bias free
-east and cheap to implement for small populations and samples
-each sampling unit has an equal chance of being selected
3 disadvantages of random sampling?
-not suitable when population size Is large
-sample may not accurately reflect the population
-sampling frame is needed
2 advantages of systematic sampling?
-simple and quick to use
-suitable for large samples and populations
2 disadvantages of systematic sampling?
-sampling frame is needed
-can introduce bias or the sampling frame is small and not random as patterns can be picked up in the data
Describe systematic sampling…
Required elements chosen at regular intervals from an ordered list
-size n is needed each item numbered randomly 1 to N
Pick every Kth element
2 advantages of stratified sampling?
-sample accurately reflects population structure
-guarantees proportional representation or groups within population
