Stats Definitions Flashcards
What is the definition of a population?
It is the set of items of interest
What is raw data?
Information obtained from a population is known as raw data.
What is a census?
A census is measuring and observing every member of a population.
Advantages of a census
Results should be completely accurate.
Disadvantages of a census.
- Time consuming
- Expensive
- Cannot be used for collecting data when destroying a member in the population.
What is a sample?
It is a portion of the whole population which is used to collect data.
Advantages of sampling.
Less time consuming
can be used when the data collection involves destroying of items.
Disadvantages of sampling.
Data may not be as accurate.
What is a sampling unit?
Individual units of a population are known as sampling units.
What is a sampling frame?
It is the list of sampling units.
What is simple random sampling?
a simple random sample size of n is one where every sample of size n has an equal change of being selected.
** A method of random sampling **
Advantages of simple random sampling.
Free of bias
easy and cheap
Disadvantages of simple random sampling.
- Sampling frame needed.
- Not suitable for large samples.
What is systamatic sampling?
The required elements are chosen at regular intervals from an ordered list.
** A method of random sampling **
Advantages of systematic sampling.
Simple and quick to use
Suitable for large samples
Disadvantages of systematic sampling?
A sampling frame is needed.
Bias introduced if sampling frame is not random.
What is stratified sampling?
The population is divided into mutually exclusive strata and a random sample is taken from each.
** A method of random sampling **
Advantages of stratified sampling.
Sample accurately reflects the population.
Disadvantages of statified sampling.
Population must be clearly classified into distinct data (this is time consuming)
What is quota sampling?
an interviewer or researcher selects a sample that reflects the characteristics of the whole population.
** a non-random sampling method **
Advantages of quota sampling.
No sampling frame needed
Efficient
cheap.
Disadvantages of quota sampling.
- population must be divided into groups which be costly.
- Can intoduce bias.
What is opportunity sampling?
Sample is taken from people who are available at the time of study and who meets the criteria you are looking for.
Advantages of opportunity sampling.
easy to carry out
cheap
