Year 1 Data Collection Flashcards
(43 cards)
What is a population
Whole set of items that are of interest to
What is a census
Observes or measures every member of a 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
Advantages and disadvantages of census vs sample
advantages:
Census : - Gives a completely accurate result
Sample: - less time consuming and expensive than a census
- fewer people have to respond
- less data to process than in a census
Disadvantages:
Census: - time consuming and expensive
- can’t be used when the testing process destroys the item
- hard to process large quantity of data
Sample: - data may not be as accurate
- sample may not be large enough to give info 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 are individually named or numbered to form a list of
What is random sampling and give the 3 types
Every member has equal chance of being selected. Sample should therefore be representative of the population. Helps to remove bias from a sample. 3 methods of random sampling are simple random, systematic sampling and stratified sampling
What is a simple random sample and what is required to carry it out
Simple random sample of size n is one where every sample of size n has an equal chance of being selected. U need a sampling frame
What is systematic sampling
Required elements chosen at regular intervals from an ordered list
What is stratified sampling
Population divided into mutually exclusive data and a random sample is taken from each. Proportion of each strata sample should be the same
Formula to calculate number of people to sample from each stratum
Number sampled in a stratum = (number in stratum/ number in population) x overall sample size
Advantages and disadvantages of simple random
Advantages:
- free of bias
- easy and cheap to implement for small populations
- each sampling unit has a known and equal chance of being selected
Disadvantages:
- not suitable when population or sample size is large
- sampling frame is needed
Advantages vs disadvantages of systematic
Advantages:
- simple and quick to use
- suitable for large samples and populations
Disadvantages:
- sampling frame needed
- can introduce bias if sampling frame isn’t random
Advantages vs disadvantages of stratified
Advantages:
- sample accurately reflects population structure
- guarantees proportional representation of groups within a population
Disadvantages:
- population must be clearly classified into distinct data
- selection within each stratum suffered from same disadvantages as simple random
2 types of non random sampling
Quota and opportunity sampling
What is quota sampling
Interviewer or researcher selects a sample that reflects characteristics of whole population
What is opportunity sampling
Consists of taking sample from people who are available at the time of study and fit the criteria you are looking for
Advantages vs disadvantages of quota
Advantages:
- allows a small sample to still be representative of population
- no sampling frame required
- quick, easy and inexpensive
- allows for easy compassion between different groups within a population
Disadvantages:
- non random sampling can introduce bias
- population must be divided into groups which can be costly and inaccurate
- increasing scope of study increases number of groups which adds time and expense
- non responses are not recorded as such
Advantages vs disadvantages of opportunity
Advantages:
- easy to carry out
- inexpensive
Disadvantages:
- unlikely to provide representative sample
-highly dependent on individual researcher
What is quantitative data
Data associated with numerical observations
What is qualitative data
Associated with non numerical observations and descriptive
What is a continuous variable
Can take any value in a given range
What is a discrete variable
Variable that can only take specific values in a given range
