Sampling

Question 1

What is sampling?

Answer 1

Choosing some members of a population to collect data on instead of the whole population

Question 2

What are the advantages of sampling (when compared to a census)?

Answer 2

-Quicker
-Cheaper
-Usually more practical

Question 3

What are the disadvantages of using sampling compared to a census?

Answer 3

-Less accurate
-Possibly biased as data isn’t collected on the whole population
-Doesn’t give data on the full population

Question 4

What is random sampling?

Answer 4

A type of sampling in which every member/item within a population has an equal chance of being chosen

Question 5

What are the advantages of random sampling?

Answer 5

Completely unbiased so the sample should be representative of the whole population

Question 6

What are the disadvantages of random sampling?

Answer 6

-May be impossible to list the whole population
-May be impossible to access the whole population
-It is not always practical/convenient (such as if the members are spread over a large area, so the researcher would have to travel far)

Question 7

What are the stages of simple random sampling?

Answer 7

1) Assign a number to each member of the sample frame
2) Use a computer, calculator, dice etc. to create a list of random numbers (as many as you need for the sample), ignoring repeats
3) Match the generated numbers to the numbers assigned to each member of the sample frame to create the sample

Question 8

What is stratified sampling?

Answer 8

A method of sampling that gives each group in a sample an amount of representation that is proportional to its size

Question 9

What are the stages of stratified sampling?

Answer 9

1) Split the population into the desired groups (such as age, gender etc.)
2) Calculate the number you should sample from each group using:
(number in category/total number) x sample size
3) use random sampling to choose the members of the groups to sample

Question 10

What are the advantages of stratified sampling?

Answer 10

-If there are easy to define categories in the population, it is likely to be representative
-You can compare the results from the different groups

Question 11

What are the disadvantages of stratified sampling?

Answer 11

-Expensive due to the extra detail needed
-Can be time-consuming
-Useless if there are no definitive groups or hard to define groups

Question 12

What is cluster sampling?

Answer 12

A method of sampling in which a random sample of small groups (clusters) is selected and every member within the cluster is sampled

Question 13

What is cluster sampling usually based off of?

Answer 13

Location (e.g. towns)

Question 14

What are the advantages of cluster sampling?

Answer 14

-Convenient
-Saves time when compared to sampling in which the population is spread out over a large area so the researcher has to travel far

Question 15

What are the disadvantages of cluster sampling?

Answer 15

It is easy to get a biased sample because:
-people in the same area may have similar opinions
-sampled clusters may be similar to each other

Question 16

What is systematic sampling?

Answer 16

Sampling by choosing a starting point and then sampling at regular intervals after that (every nth term)

Question 17

What are the advantages of systematic sampling?

Answer 17

-Should produce an unbiased sample
-Can be done by machines, making it less time consuming

Question 18

What are the disadvantages of systematic sampling?

Answer 18

-Some members have no chance of being chosen so isn’t strictly random
-If the nth term coincides with a pattern, the sample will be biased

For example, if every tenth item is faulty, sampling every 9th would show no faults but every 10th shows all faults

Question 19

What is quota sampling?

Answer 19

The population is split into groups (e.g. age, gender) and a certain number is interviewed from each group

Question 20

What are the advantages of quota sampling?

Answer 20

-Quick
-Represents the different groups
-Can be done without a sample frame

Question 21

What are the disadvantages of quota sampling?

Answer 21

-not random as the interviewer chooses who to sample so can be unrepresentative
-can be biased
-people may refuse to be interviewed and they may for a certain shared reason, removing that viewpoint from the sample

Question 22

What is opportunity/convenience sampling?

Answer 22

A sample is taken from a section of the population who are present at one time and in one place

Question 23

What are the advantages of opportunity/convenience sampling?

Answer 23

-convenient as the place and time suits the interviewer
-no sample frame is needed

Question 24

What are the disadvantages of opportunity/conveniece sampling?

Answer 24

-not representative of the whole population
-can be very biased

Question 25

What is judgement sampling?

Answer 25

A method of sampling in which the researcher picks people who they think represent the whole population

Question 26

What is judgement sampling mostly used for?

Answer 26

Researching topics that are quite obscure or specific

Question 27

What are the advantages of judgement sampling?

Answer 27

-quick
-may be the only suitable method (especially if very obscure or specific)

Question 28

What are the disadvantages of judgement sampling?

Answer 28

-can be biased especially if the researcher wants a particular result
-researcher may be unreliable so must have good knowledge and judgement of the population