types of sampling

Question 1

what is a random sample?

Answer 1

when every person/item in the population has an equal chance of being selected

Question 2

what are some different ways of carrying out a random sample?

Answer 2

pick numbers/names out of a hat, spin the wheel or use a random number generator on your computer/calculator

Question 3

what are some advantages of random sampling?

Answer 3

(1) random sampling is unbiased
(2) the sample is representative of the entire population as they all had an equal chance of being chosen

Question 4

what are some disadvantages of random sampling?

Answer 4

(1) need a full population list - inconvenient
(2) could be expensive and time consuming
(3) needs a large sample size

Question 5

what is stratified sampling?

Answer 5

the size of each strata (group) in the sample is in proportion to the sizes of the strata in the population. e.g. if group A accounts for 10% of the population, in the sample group A will also be 10% of the sample size.

Question 6

what are the advantages of stratified sampling?

Answer 6

(1) sample represents the population fairly as the sample is in proportion to the population
(2) best used for populations of groups with unequal sizes

Question 7

what are the disadvantages of stratified sampling?

Answer 7

(1) time consuming

Question 8

what is systematic sampling?

Answer 8

choosing items in the population at regular intervals

Question 9

what are the disadvantages of systematic sampling?

Answer 9

(1) not strictly a random sample as some members of the population cannot be chosen

Question 10

what are the advantages of systematic sampling?

Answer 10

(1) population is evenly sampled
(2) can be carried out by a machine
(3) sample is easy to select

Question 11

what is cluster sampling?

Answer 11

the population is divided into natural groups, groups are chosen at random and every member of groups are sampled.

Question 12

what are the advantages of cluster sampling?

Answer 12

(1) economically efficient - less resources are required
(2) can be representative if lots of small clusters are sampled

Question 13

what are the disadvantages of cluster sampling?

Answer 13

(1) may not be representative, may lead to bias

Question 14

what is quota sampling?

Answer 14

population is grouped by characteristics and a fixed amount is sampled from each group

Question 15

what are the advantages of quota sampling?

Answer 15

(1) quick to use
(2) cheap
(3) do not need sample frame or full list of the population

Question 16

what are the disadvantages of quota sampling?

Answer 16

(1) NOT RANDOM!!! - biased, they choose who will be in the sample so there isn’t an equal chance.

Question 17

what is opportunity sampling?

Answer 17

using the people or items that are available at the time.

Question 18

what are the advantages of opportunity sampling?

Answer 18

(1) quick
(2) cheap
(3) easy

Question 19

what are the disadvantages of opportunity sampling?

Answer 19

(1) NOT RANDOM - hasn’t been selected fairly, so no equal chance of being chosen.

Question 20

what is judgement sampling?

Answer 20

when the researcher uses their own judgement to select a sample that they deem is representative of the entire population.

Question 21

what are the advantages of judgement sampling?

Answer 21

(1) quick
(2) easy

Question 22

what are the disadvantages of judgement sampling?

Answer 22

(1) NOT RANDOM
(2) may be biased and unrepresentative