edwinesosa's version from 2015-05-14 17:51


Question Answer
what is a populationA whole set of items that are of interest
what is a censusevery member of population observed
what is a samplea small portion of the population is observed
advantage of a censusaccurate
cons of a censuscost + time + when testing process if for destruction + too much info makes it hard to process
cons of samplemay not be large enough to give info about small sub groups
what is simple random samplingwhen every other sample of size n has an equal chance of being selected
what is a sampling framea list identifying every single possible sampling unit that could be included in the sample
pros of simple random samplingcheap and easy + each unit included only once + a standard formula can be used to analyse the results
how does a random number sample workassign each element of the sampling frame a number, and the numbers of the required elements are selected by using random number tables
pros of random number samplingnumbers are truly random and free from bias + each number has a known equal chance of selection + easy
cons of random number samplingnot suitable with large population size
what is lottery samplingnames in a hat
pros of lottery samplingtickets drawn at random + easy + each ticket has known chance of selection
cons of lottery samplingnot suitable with large population + a sampling frame needed
systematic samplingthe required elements are chosen at regular intervals from a ordered list, with interval being population size/sample size, first item selected is random and less than k
pros of systematic samplingcan use with large population + simple
cons of systematic samplongcan introduce bias (k is 12 when sampling months of the year) + only random if ordered list truly random
stratified samplingthe population is divided into mutually exlusive strata and a random sample is taken from each
pros of stratified samplingmore accurate estimates than simple random + reflects the population structure
Quota samplingthe population is divided into groups in terms of gender, class etc. the number of people in each group is set to try and reflect the groups proportion in the whole population. the interviewer selects the actual sampling units
pros of quota samplingIt enables fieldwork to be done quickly because a representative sample can be achieved with a small sample size + cheap +easy
cons of quotanot possible to estimate sampling errors + interviewer has to choose the respondants and may not judge characteristics well + non respondents not recorded + can introduce interviewer bias in who is included
pros of primary dataknown collection method + known accuracy + exact data needed collected
pros secondarycheap + large amount of data + much of data has been collected for years and can be used to plot trends
cons secondarybias not always recognised + may be in a hard to use form