chapter 1 - data collection Flashcards
census
observes or measures every member of the population
sample
selection of observations taken from a subset of the population which Is used to find out information about the population as a whole
advantages of a census
gives a completely accurate result
disadvantages of a census
- time consuming
-expensive
-cannot be used when testing destroys the item
-hard to process large quantity of data
advantages of a sample
- less time consuming and expensive than a census
- fewer people have to respond
- less data to process than a census
disadvantages of a sample
- data may not be accurate
-sample may not be large enough to give information about small subgroups of the population
simple random sample
every member of the population has an equal chance of being selected
advantages of simple random sampling
- free of bias
- easy and cheap to implement for small populations and small samples
-each sampling unit has a known and equal chance of selection
disadvantages of simple random sampling
-not suitable when the population size or sample size is large
-sampling frame is needed
systematic sampling
required elements are chosen at regular intervals in an ordered list
stratified sampling
population is divided into mutually exclusive strata (e.g males and females) and a random sample is taken from each
stratified sampling formula
(number in each stratum/population size) x overall sample size
advantages of systematic sampling
- simple and quick
-suitable for large samples and large populations
disadvantages of systematic sampling
- sampling frame is needed
-introduce bias if the sampling frame is not random
advantages of stratified sampling
-sample accurately reflects the population structure
- guarantees proportional representation of groups within a population
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
quota sampling
interviewer or researcher selects a sample that reflects the characteristics of the whole population
opportunity sampling
taking a sample of people who are available at the time the study is carried out and who fit the criteria you are looking for
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 different groups within a population
disadvantages of quota sampling
- non random sampling can introduce bias
-population must be divided into groups, which can be costly or inaccurate
-increasing scope of study increases number of groups, which adds time and expense
-non-responses are not recorded as such
advantages of opportunity sampling
-easy to carry out
-inexpensive
disadvantages of opportunity sampling
-unlikely to provide a representative sample
-highly dependent on individual researcher
