sampling techniques

Question 1

what are the stages of the sampling process ?

Answer 1

stage 1 : define target population 
stage 2: select sampling frame 
stage 3: choosing a sampling technique 
stage 4: determine sample size
stage 5: collect data 
stage 6: asses response rate

Question 2

what is a sampling frame ?

Answer 2

a list of the actual cases from which sample will be drawn

Question 3

how is a sampling unit defined?

Answer 3

inclusion criteria

exclusion criteria

Question 4

what are the two main types of sampling techniques ?

Answer 4

random sampling

non-random sampling

Question 5

what does probability or random sampling mean ?

Answer 5

means that the sampling unit in the population has an equal chance of being included in the sample

Question 6

what is the first step in random sampling ?

Answer 6

constructing a sampling frame first

Question 7

what is the greatest advantage of probability sampling or random sampling ?

Answer 7

free from bias

Question 8

what are the types of random sampling ?

Answer 8

simple random sampling 
systematic random sampling 
stratified random sampling
cluster sampling 
multi stage sampling

Question 9

when is it best to use systematic random sampling ?

Answer 9

if the study population is homogenous and you have a complete list of all the units

Question 10

what is the method of systematic random sampling ?

Answer 10

1. population size is to be determined
2. sample size needs to be determined
   divide pop size by sample size to get the interval
   choose a number within the interval
   then add the interval to that number and so on

Question 11

what is the disadvantage of systematic random sampling ?

Answer 11

risk of bias due to cyclic phenomenon

Question 12

what is stratified random sampling ?

Answer 12

the population is separated into strata according to a certain criteria and a random sample is taken from each group
the sub samples are then joined to form a total sample for the study

Question 13

when is stratified random sampling used ?

Answer 13

when there is a lot of variation within a population

Question 14

what is cluster sampling ?

Answer 14

whole population is divided into clusters or groups, then a random sample is taken from these clusters

Question 15

when is it best to use cluster sampling ?

Answer 15

for researchers whose subjects are fragmented over a large geographical are as it saves time and money

Question 16

what is non probability sampling often associated with ?

Answer 16

case study research design and qualitative research

Question 17

what are the types of non probability sampling ?

Answer 17

quota sampling
snowball sampling
convenience sampling
judgemental sampling

Question 18

what is quota sampling ?

Answer 18

participants are chosen on the basis of predetermined characteristics

Question 19

what is snowball sampling ?

Answer 19

non random sampling that uses a few cases to help encourage other cases to take part in a study

Question 20

what is convenience sampling ?

Answer 20

selecting participants because they are often readily and easily available

Question 21

what is judgemental sampling ?

Answer 21

particular persons or events are selected deliberately in order to provide important information that cannot be obtained from other choices

Question 22

what is the relationship between sample size and sampling error ?

Answer 22

as the sample size increases the sampling error decreases

Question 23

what are the factors that must be taken into consideration when calculating sample size ?

Answer 23

type 1 error
type 2 error
the power of a study

Question 24

what is a type 1 error ?

Answer 24

the risk of a false positive result (( chance of detecting a statistically significant difference when there is no real difference)

Question 25

what is a type 2 error ?

Answer 25

the risk of a false negative result ( the likelihood of not detecting a significant difference when there is a difference)

Question 26

what is the power of a study ?

Answer 26

the probability of not making a type 2 error

Question 27

what determines the power of a study ?

Answer 27

• the frequency of the condition

- the magnitude of the effect

Question 28

what does the sample size reflect ?

Answer 28

the number of obtained responses and not necessarily the number of questionnaires distributed

Question 29

what is the response rate ?

Answer 29

the number of cases agreeing to take part in the study