Sampling

Question 1

Sampling types

Answer 1

Opportunity sampling
Random sampling
Systematic sampling
Stratified sampling
Volunteer sampling

Question 2

Opportunity sampling

Answer 2

Recruit those people who are most convenient or most available
Eg people walking by you in the street

str: easiest and least time consuming bc less time to locate sample

lim: biased bc sample is drawn from a small part of the population

Question 3

Random sample

Answer 3

Each item in a population has an equal chance of being selected

Techniques:
Lottery method=
1) obtain a list of all ppl in the population
2) put all the names in a lottery barrel or hat
3) select the names required

Random number generator
1) number every member of the population
2) using of example, Microsoft excel tyoe= RAND(100) to get a random number between 1-100

Random numer table=
1) give every member of pop a number
2) starting position in the table is determuned blidndly by placing finger anywhere

Str: unbiased- all members of target pop have equal chnce

Lim: Time consuming- need to have a list of all members of pop and contact them all

Question 4

Stratified sample

Answer 4

Subgroups within a pop are identified and participants are obtained from each of the strata in the proportion to their occurence in the pop. Selection from the strata is fone using a random technique.

Str: Likely to be more rep than other methods bc proportional and representative

Lim: Very time consuming to idently subgrouos and randomly select and contact

Question 5

Systematic sample

Answer 5

Use a predetermined system to select participants
eg selecting every nth person from a phonebook
The numerical interval is applied consistently

Str: Unbiased as partiipants selected from an objective system

Lim: Not trult unbiased unless you select a number using a random method ans start w this person and then select every nth person

Question 6

Volunteer sample

Answer 6

Advertise for participants
eg newspaper, noticeboard, internet

str: Gives access to a wide vafriety of participants which may makle the sample more rep

Lim: Volunteer bias Sample is biased in other ways as participasnts are likely to be more motivated or have more time on their hands or theyre broke