Research Methods : Sampling Flashcards
population
large group of people researcher intersted in studying e.g women in thirties
why is population aka target population
subset of general pop
why is it impossible to include all memebers of target populaiton
economical and practical reasons
as its not economci and practical to include all members of TP what do r do
selects sample
ideally sample drawn is
Representative of the target population
why ideally is sample drawn representative of the target population
generalisation of findings becoming practical
why is it difficult to represent populations in any sample
inevitably diverse nature of pop of people e.g gender , age .life experiences
inevitability vast of samples include
degree of bias
samples are selected using
sampling technique
sampling techs aim to produce
a representative sample
random sample
all mems of TP have equal chance of being selected
outline steps of getting a random sample
get list of all names of TP
assing names a number
actual sample selected using lottery method . e.g picking #out of hat
Systematic sample
every nth mem of TP selected
give example of systematic sampling
every 5th student in a class
sampling frame
list of people in TP organised e.g alphabetical
how do you do systematic sampling
establish sampling frame
nominate sampling sustem (e.g every 6th person)
begin from randomly determined start
work through sampling frame till complete
why do you begin from a randomly detrmined start
reduce bias
stratified sampling
composition of sample reflects proportions of people in certain subgroups in TP / Wider population
outline how to carry out startified sampling
identify diff starta that make up population
proportions for sample to be representative worked out
pt make up each starta selected through random sampling
opportunity sampling
researcher select anyone willing and available (opportunity sample )
Why would you use opportunity sampple
representative samples of TM difficult to obtain
t/f researcher taking whoever available at the time on street for a study is OS
T
Volunteer sample
pt selecting themselves to be pt of a sample
volunteer sample aka
self - selection
how could you select volunteer sample
researcher places ad in a newspaper
pt raise hand when researcher asks
-ve of all samples
pt may refuse to take part meainng you end up more like a vol samp
+ve of rando sampling (bias)
potentially unbiased so C/EV equally divided between different groups
enhancing IV
-VE or rando sampling (time)
difficult
time consuming to conduct
complete list of tp - may be difficult to obtain
in terms of random sampling even though unbiased you may still
laws of prob suggest
but still possible
end up with unrepresentative sample
laws of probability suggest random sampling likely to produce more representative sample than op sample
but still possible random methods select 20 female psych teachers from lancashire called joyce
strenght of systematic sample - objectivity
once system for selection been est …
its obejctive
once system for selection been established researcher has no influence over who’s chosen - even more the case if start is randomly selected)
limitation of systematicv sampling 2 ish
tiktok
time consuming (like random)
in the end pt may refuse to take part resulting in a voluntter sample
strenght of startified sample - reoresentaiton
produces representative sample as designed to accuraltey reflect composition of population therefore generalisation of findigns becomes more possible
limitation of stratified sample- perfection
not perfect cuz
identified strata cannot reflect all the ways people are different so compelte represetnation of target population isn’t possible
(therfore coplete generalisation not possible)
strenht opp sample - c
convenient , much less csotly int erms of time and money than e,g random samplign , as list of members of target population not required
and theres no need to divide population into diff strata like stratified sampling
negative opp sampele - 2 forms of bias
sample unrepresentaitve of target population as its drawn from a very sepcific area e.g one street in one town
therfore findings cant be genralsied to target population
researcher has complete control over selection of pt and may show researcerh bias by avoiding people they dont liek look of or choosing people they do
strengths volunteer sampel - ease
enage
its easy as requires minimal input from researcher (as tehy come to you)so less time consumiing than other forms of sampling
researcher ends up with pt whore more engaged , more so than someone stopped in street
why is volunteer bias a problem
asking for volunteers may attract a certain profile of person e.g more curious and liekly to try please
e sample may be biased as the type of student who volunteers may have
differing traits to the general population, for example they may be more extrover
not necessarily reflect the population
therfore results of study not generalisable to wider pop
