se notation Flashcards
population
the whole set of items that are of interest
census
observers or measures every member of a population
a sample
is a selection of observations taken from a subset of the population which is used to find out information about the population
indiuviual units of a population are know as what
sampling units
spampling frame
often sampling units of a population are individually named or numbered to form a list
a simple random sample
size n is one where every sample size n has an equal chance of being selected
systematic sampling
the required element are chosen at regular intervals from an ordered lists
quota sampling
an interviewer or researcher selects a sample that reflects the characterises of the whole population
stratified sampling
the population is divided into mutually exclusive strata and a random sample is taken from each
number sampled in a stratum formula
number in stratum divided by population x overall sample size
advantage of census
it should give a completely accurate result
disadvantage of census
time consuming and expensive
cannot be used when the testing process destroys the item
hard to process large quantity of data
advantage of sample
fewer people have top respond
less data to process than in a census
less time conbsuyming and expensive than a census
disadvantage of sample
the data may not be accurate
may not be large enough to give info about small sub groups of population
advantage of simple random sampling
free of bias
easy and cheap to implement for small population and small samples
each sampling unit has a known and equal chance of selection
disadvantage
not suitable when population size or the sample size is large as it its potentially time consuming, disruptive and expensive
a sampling frame is needed
systemic sampling advantage
simple and quick to use
suitable for large samples and large populations
systemic sampling disadvantage
a sampling frame needed
it can introduce bias if the sampling frame is not random
stratified sampling advantage
sample accuracy reflects the population structure
grates proptionasl representation of groups within population
stratified sampling disadvantage
population must be creamy classified into distinct strata
selection within each stratum suffers from the same disadvantage as simple random sampling
quota sampling advantage
allows a small sample to still be repressive go the population
no sampling frame needed
quick easy and inexpensive
allows for easy comparison between different groups within a population
quota sampling disadvantage
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
opportunity sampling advantage
easy to carry out
inexpensive
opportunity sampling disadvantage
unlikely to provide a representative sampling
high;y dependent on indivuial researcher
