Types Of Sampling

Question 1

How would you carry out a simple random sample?

Answer 1

Obtain a sample frame. Number all units with an identifying number. Use random number generator to select the numbers, which correlate units.

Question 2

Advantages of a simple random sample.

Answer 2

Bias free.
Cheap and easy.
Every number has known and equal selection chance

Question 3

Disadvantages of a random sample.

Answer 3

Not suitable in very large population as the simple random sample often wouldn’t be fully representative.
Sampling frame is required.

Question 4

How to carry out systematic sample?

Answer 4

. Obtain sampling frame consisting of the people in the first interval.
. Assign each a number, and using a random number generator, select the first person.
. From here, select units at regular intervals eg. Every tenth person.

Question 5

Advantages of systematic sample

Answer 5

Random so avoids bias.
Suitable for large samples/populations

Question 6

Disadvantages of systematic sample.

Answer 6

Need a sampling frame.

Question 7

Stratified sampling

Answer 7

Population divided into groups (stratas) which can be proportionally sized to represent the entire population.
Random sample within each strata

Question 8

Advantages of stratified sampling

Answer 8

. Useful in a large population which easily divides.
. Proportionally representative.
. Reflects structure of population.

Question 9

Disadvantages of stratified sampling.

Answer 9

. Population must divide clearly into groups
. Groups may not be mutually exclusive
. Sampling frame is required.

Question 10

How would you carry out a Quota sample?

Answer 10

Population is divided into groups based on its characteristics.
Each group is given a set number of units (quota), to reflect the population proportionally.
Interviewer selects units until each quota is reached.

Question 11

Advantages of quota sampling

Answer 11

Representative of population.
No sampling frame required.
Quick, easy and inexpensive.
Easy to compare results between groups.

Question 12

Disadvantages of quota sampling.

Answer 12

Not random as interviewer selects the people. Meaning potential bias.
Dividing population into groups not always accurate and groups may not be mutually exclusive.
Non responses are not recorded.

Question 13

How would an opportunity sample be carried out?

Answer 13

Interviewer waits at a set location (eg. In a city shopping centre). Criteria set for units, and the interviewer selects units who meet the criteria.

Question 14

Advantages of opportunity sampling.

Answer 14

Very easy to carry out
Inexpensive

Question 15

Disadvantages of opportunity sampling

Answer 15

Unlikely to be representative eg. Certain groups of people may not go to the location of the sample being recorded.
Highly dependent on individual researcher so can lead to bias.