Types of sampling 11.2

Question 1

what is meant by sampling

Answer 1

• method of investigating the abundance and distribution of species and populations.

Question 2

what is the function of sampling

Answer 2

• used to estimate number of organisms in area without having to count them all.
• used to measure frequecny of characteristic in population

Question 3

How can sampling be used to measure the characteristics of an organism

Answer 3

• by measuring characteristic of many organisms and calculating average can get accurate general value

Question 4

what are the 2 types of sampling

Answer 4

random and non-random

Question 5

what is meant by random sampling

Answer 5

• each individual in the population has equal likelihood of selection

Question 6

what are the steps of taking a random sample

Answer 6

1) Mark out a grid using 2 tape measures laid at right angles
2) Use random numbers to determine the x and y coordinate on your grid
3) Take a sample at each of the coordinate pairs generated

Question 7

what is meant by non-random sampling

Answer 7

the sample is not chosen at random.

Question 8

What are the 3 methods of non-random sampling

Answer 8

• Opportunistic
• Stratified
• systematic

Question 9

What is Opportunistic sampling

Answer 9

• uses organisms that are conveniently available
• weakest from of sampling as may not represent population well

Question 10

what is Stratified sampling

Answer 10

• populations can be divided into strata (sub groups).
• random sample taken from each of these Strata proportional to its sizein overall population

Question 11

what is systematic sampling

Answer 11

• areas within habitat are seperated and sampled independently

Question 12

what does a line transect involve in terms of sampling

Answer 12

• marking a line along the ground between 2 poles and taking samples at specified points
• can be describing organisms that touch the line (within distance from line)

Question 13

what does a belt transect involve interms of sampling

Answer 13

• 2 parallel lines are marked, samples are taken of the area between the 2 lines

Question 14

what are some things that could effect the reliability of sampling

Answer 14

• Sampling bias
• chance

Question 15

• How can sampling bias effect the reliability of sampling
• How can bias be removed from the sampling process

Answer 15

• can lead to results that dont represent population
  ^segments may be excluded
• bias can be accidently or deliberate
• bias reduced when using random sampling
  ^where human involvement in choosing the samples is removed

Question 16

how can chance be minimised while sampling

Answer 16

• Larger sample sizes minimize the impact of chance on sampling
• ^increases reliability by reducing possibility of chance influencing the outcome.