Chapter 1 Flashcards
What is population?
The whole set of items that are of interest
What is a census?
A study that observes/measures every member of the population.
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 is are sampling units?
Individual units of a population.
What is a sample frame?
A list formed by sampling units of a population are individually named or numbered.
What is 1 advantage of a census?
It should give completely accurate results.
What are 3 disadvantages of a cencus?
- Time consuming and expensive
- Can not be used when testing process involves destruction
- Large volume of data to process
What are 3 advantages to sampling?
- Cheaper
- Quicker
- Less data to process
What are 2 disadvantages of sampling?
- Data may not be accurate
- Data may not be large enough to represent small sub-groups
What does random sampling allow?
Allows every member of the population to have an equal chance of being selected (removes bias).
What is simple random sampling?
Every sample of size n is one where every sample of size n has an equal chance of being selected.
What is systematic sampling?
Required elements are chosen at regular intervals from an ordered list. Only truly random if first number is chosen randomly.
What is stratified sampling?
The population is divided into mutually exclusive strata and a random sample is taken from each.
What is a stratum?
A subset (part) of the population which is being sampled.
How do you calculate the number sampled in a stratum?
= (number in stratum / number in population) x overall sample size
What are 4 advantages of simple random sampling?
- Unbiased
- Each member of the population has the same chance of being chosen
- Easy and cheap to implement for small populations
- Data from a random sample can be used in statistical calculation
What are 2 disadvantages of simple random sampling?
- A sampling frame is needed
- The sample may not be representative of all sections of the population
What are 3 advantages of systematic sampling?
- Unbiased
- Each member of the population has the same chance of being chosen
- Usually easy to carry out
What is 1 disadvantage of systematic sampling?
- A sampling frame is needed, unless the population appears in a sequence like items on a production line.
What is quota sampling?
When the researcher selects a sample that reflects the characteristics of the whole population.
What is opportunity sampling?
Taking the sample from people who are available at the time the study is carried out and who fits the criteria you are looking for.
What are 2 advantages of quota sampling?
- No sampling frame is needed
- Each section of the population is fairly represented
What is 1 disadvantage of quota sampling?
- can introduce bias.
What are 2 advantages of opportunity sampling?
- No sampling frame is needed
- Easy and cheap to carry out
What are 3 disadvantages of opportunity sampling?
- May introduce bias
- Unlikely to produce a representative sample
- Highly dependent on individual researcher
What are qualitative variables?
Non-numerical variables.
What are quantitative variables?
Numerical variables
What is a discrete variable?
can only take certain values (like number of people or shoe size) - this means there are ‘gaps’ between possible values.
What is a continuous variable?
Can take any value within a particular range (like height or mass) - this means there are no gaps between possible values.
