Sampling

Question 1

point sampling

Answer 1

e.g. names on a list or coordinates on a map

Question 2

linear sampling

Answer 2

e.g. sampling along a line such as transect along dunes or a road

Question 3

areal sampling

Answer 3

e.g. usually in investigation surveys where a quadrat is used to measure the contents of a 1 metre square area or it could be a grid square on a map

Question 4

random sampling description

Answer 4

random number tables to select points e.g. sampling stone size in a river

Question 5

advantages of random sampling

Answer 5

• more statistically useful for subsequent tests, so allows follow up analysis
• no bias

Question 6

disadvantages of random sampling

Answer 6

• items can be duplicated
• easy to miss important subdivisions
• hard to ensure its truly random

Question 7

stratified sampling description

Answer 7

-when the parent population or sampling frame is made up of sub sets known as strata of known size. these sub sets make up different proportions of the total , and therefore sampling should be stratified to ensure that results are proportional and representative of the whole

Question 8

advantages of stratified sampling

Answer 8

• ensures no significant aspect of the sub sets is missed

- very flexible and applicable to most investigations

Question 9

disadvantages of stratified sampling

Answer 9

• biased
• proportions of sub sets must be known
• can’t make valid statistical inferences

Question 10

sampling definition

Answer 10

the strategy of collecting data that is representative of the whole population

Question 11

problems if the sample size is too small

Answer 11

• less reliable averages can be taken
• more affected by anomalies
• biased
• anything less than 30 doesn’t provide valid conclusions
• statistical tests can’t be done
• might miss something
• patterns/trends are disorted