sampling techniques Flashcards
what are the five types of sampling?
opportunity random stratified systematic volunteer
what is the process of an opportunity sample?
recruiting those people who are most convenient or most available. for example people walk by you on the street or students at your school
what are some strengths and weaknesses of opportunity sampling?
+easiest method as you can use the first suitable participants you can find.
-inevitable biased as the sample is drawn from a small part of the population.
what is the process of a random sampling technique?
lottery method:
draw numbers or names out of a ‘hat’
1. obtain list of all people in (target) population
2.put names in lottery barrel or hat
3.select the number or names required
random number table:
use a printed table of random numbers
1. every member or (target population) is given a number
2. the starting position is chosen blindly by placing your finger anywhere.
3. if population is less than 100, you need 2 digit numbers so you read off the table the first two digit numbers of each number.
what are the strengths and limitations of a random sampling method?
+unbiased, all members of target population have an equal chance of selection.
-need to have a number for all people in target population and must contact them after which takes time
how is a stratified sampling method achieved?
subgroups or starts within a population are identified. participants are obtained from each of the strata’s in proportion to their occurrence in the population. selection from strata’s are done using random sampling techniques.
what are some strengths and limitations of stratified sampling techniques.
+likely to be more representative than other methods because there is a proportional and randomly selected representation of sub-groups.
-very time consuming to identify subgroups, then randomly select participants and contact them.
how is a systematic sampling technique achieved?
uses a predetermined system to select participants, such as selecting every nth person from a phone book. the numerical interval is applied consistently.
what are the strengths and limitations of systematic sampling?
+unbiased as participants are selected using an objective system.
-not truly unbiased/random unless you select the number using a random method and start with this person, and then select every nth person.
what is a volunteer sample?
advertised in a newspaper or a noticeboard, and people put themselves forward.
what are some strengths and limitations of a volunteer sample?
+gives access to variety of people which may make the sample more representative and less biased.
-sample is biased in other ways as the sam[le is more likely to be more highly motivated for money or something to do so will lead to a volunteer bias (certain characteristics like more motivated so can make the study distorted.)
