Data collection (Stats year 1 - chapter 1) Flashcards
(27 cards)
What is a census?
Observes or measures every member of a population.
What are advantages of using a census?
It should give a completely accurate result.
What are disadvantages of using a census?
Time consuming and expensive.
Cannot be used when the testing process destroys the item.
Hard to process large quantities of data.
What is a sample?
A selection of observations taken from a subset of the population which is used to find out information about the population as a whole.
What are advantages of using a sample?
Less time consuming and expensive than a census.
Fewer people have to respond.
Less data to process than in a census.
What are disadvantages of using a census?
The data may not be as accurate.
The sample may not be large enough to give information about small sub-groups of the population.
What are sampling units?
Individual units of a population.
What is a sampling frame?
Sampling units of a population that are individually named or numbered to form a list.
What is a simple random sample?
A simple random sample of size ‘n’ is one where every sample of size ‘n’ has an equal chance of being selected.
What are advantages of simple random sampling?
Free of bias
Easy and cheap to implement for small populations and samples.
Each sampling unit has a known and equal chance of selection.
What are some disadvantages of simple random sampling?
Not suitable when the population size of the sample size is large.
Sampling frame is needed.
What is systematic sampling?
In systematic sampling the required elements are chosen at regular intervals from an ordered list.
What are some advantages of systematic sampling?
Simple and quick to use.
Suitable for large samples and large populations.
What are some disadvantages of systematic sampling?
A sampling frame is needed.
It can introduce bias if the sampling frame is not random.
What is stratified sampling?
In stratified sampling, the population is divided into mutually exclusive strata (for example males and females) and a random sample is taken from each.
What are some advantages of using stratified sampling?
Sample accurately reflects the population structure.
Guarantees proportional representation of groups within a population.
What are some disadvantages of stratified sampling?
Population must be clearly classified into distinct strata.
Selection within each stratum suffers from the same disadvantages as simple random sampling.
What is quota sampling?
An interviewer or researcher selects a sample that reflects the characteristics of the whole population.
What are some advantages of quota sampling?
Allows a small sample to still be representative of the population.
No sampling frame required.
Quick, easy and inexpensive.
Allows for easy comparison between groups in a population.
What are some disadvantages of quota sampling?
Non random sampling can introduce bias.
Population must be divided into groups which can be costly or inaccurate.
Non responses are not recorded as such.
What is opportunity sampling?
Consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for?
What are advantages of opportunity sampling?
Easy to carry out
Inexpensive
What are disadvantages of opportunity sampling?
Unlikely to provide a representative sample.
Highly dependant on individual researcher.
What is quantitative data?
Variables or data associated with numerical observations.
