This document discusses various sampling techniques used in research. It defines random sampling as selecting samples where every member has an equal chance of being chosen. Simple random sampling involves tools like fishbowls or random number tables. Systematic sampling involves selecting every nth member from a population. Purposive sampling selects members based on the researcher's judgment. Specific techniques discussed include coning and quartering for granular materials, quadrat sampling which uses frames to sample stationary objects, belt transects which use parallel lines, and considerations for water sampling like container type and processing time.

1. Avenir,Chamique
Pacheco Gimuel
Alfred Serato

3. A subset of a population on which
the information is obtained

5. Goal: Get an accurate
picture of the population
from the sample
RANDOM SAMPLING
Equal chance of being
selected
Choose me!
Choose me!
Choose me!
Choose me!
Choose me!
Choose me! Choose me!

6. SIMPLE
RANDOM
SAMPLING
1
2
3
4
5
6
7
8
9
2
5
9

7. 1
3
6
8
10

8. 1 2 3
4 5 6
7
5
4
2

9. Tools:
1. Fishbowl/ Lots (with replacement)
2. Random Number Table
3. Random number generator in the
calculator or computer

10. Random Assignment – every participant in the
experiment has an equal chance of
being assigned to any of the
experimental or control conditions
being compared.
Random Selection – every member of population has
an equal chance of being selected to
be a member of the sample.

11. Systematic sampling

12. Systematic sampling

13. Convenience sampling

14. Purposive Sampling
The selection of a sample is based on
 previous knowledge of a population
 specific purpose of the research

15. Purposive Sampling
 different from convenience sampling
 researchers do not simply study whoever is
available
 but use their judgement to select a sample
which they believe will provide the
data they need

16.  Coning and Quartering
 Quadrat sampling
 Transect Lines
 Water Sampling

17.  Coning and Quartering
For granular or powdered samples
Procedure
• Form a conical heap
• Spread it out into a circular flat cake
• Divide the cake radially into
quarters
• Choose two opposite quarters;
combine
• Discard the other two quarters
• Repeat as many times as needed to
get desired amount

18.  Coning and Quartering
• Form a conical heap

19.  Coning and Quartering
•Spread it out into a circular flat cake

20.  Coning and Quartering
• Divide the cake radially into quarters

21.  Coning and Quartering
•Choose two opposite quarters; combine

22.  Coning and Quartering
•Discard the other two quarters
•Repeat as many times as needed to get desired
amount

23.  Quadrat sampling
-A small area of ground marked out as sample
of a larger area
Purpose: to make a detailed description and
record numerical data
For sampling objects that do not move –
vegetation or more or less sedentary animals

24.  Quadrat sampling

25.  Quadrat sampling
A frame of predetermined area –
placed on the ground
Data: number of individuals per unit area
Decisions:
- quadrat size (usually 1m x 1m)
- quadrat shape (usually square)
- where to put it
- how many quadrats
- what rules to set

26.  Quadrat sampling

27.  Quadrat sampling

28.  Quadrat sampling
Random- Throwing quadrat

29.  Quadrat sampling

30.  Quadrat sampling

31.  Quadrat sampling
Systematic- using grids
- divide the area into squares of equal sizes
- locate the quadrats by picking coordinates
randomly

32.  Quadrat sampling
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15

33.  Quadrat sampling
7
14

34. Transect Lines
- A line (usually straight) laid out on
a sampling site
-Observations are made in a systematic way
along the line
Decision:
- where to mark out the transect
- how long
- how many
- how far apart
- intervals between obseervations

35. Transect Lines

36. Transect Lines
Line Transect- individuals touching the tape
are recorded

39. -two parallel lines are marked
out,individuals between these
lines are recorded.
-similar to the line
transect
-
abundance, presence
or absence of species

41. Transect : Ladder Transect

42. Considerations
1)Type of water body.
2Tests to be performed on the sample.
3)Volume of the sample
4)Container to use
5)Cleaning procedure for container.
6)Water collection technique
7)Transporting and storage
8)How soon to process the sample

43. - Collect a sample by the hand-dip method if the stream is well mixed.
-Open a sterile bottle ;grasp the bottle near the base , with hand and arm on
downstream side of the bottle.
-Without rinsing , plunge the bottle opening downward below the water
surface. Allow the bottle to fill with the opening point slightly upward into
the current.
-Remove the bottle with the opening pointed upward toward the water and
tightly cap it, allowing about 2.5 to 5 cm of headspace.
-This procedure minimizes the collection of the surface film and avoids
contact with the streambed.

44. 1)Clean bottles and cap with dilate
non phosphate, laboratory-grade
detergent, rinse it 3 times with hot
tap and 3 times with deionized or
distilled water and sterilize it by
autoclaving.
2)Collect approximately
800mL of stream water.
3)Leave at least an inch of
headspace in the bottle to allow
adequate mixing and aeration.
4)For E.Coli: Process
the samples within 6
hours.
Store sample on ice
in cooler or
refrigerator before
processing.

46. Aczel, Amir D. 1995, Statistics and Concepts and Applications, Chicago , Richard D . Irvin
Inc.
Beach,David P. and Alvager, Torsten K.E,1992. Handbook for Scientific and Technical
Research, New Jersey, Prentice Hall.
Brace, Charles H. and Brase, Corrine P. 1995. Understandable Statistics. Fifth Edition .
Lexington, Massachussetts D.C Health and Company.
David, Fely P.,2002. Understanding and doing Research: A handbook for Beginners.Trial
Edition. Iloilo City.
Kumar, Ranjit, 1996, Research Methodology. Australia Addison Wesley Longman.
Rivera, Maximiano M. Jr. and Rivera, Roela Victoria,1996. Practical Guide to Thesis and
Dissertation Writing. Manila, Philippines.
Sevilla Consuelo,G.et.al 1998. Research Methods, Revised Edition, Manila Rex bookstore.
Field Sampling. Us geological Survey Ohio District Microbiology Laboratory. 2003.
Online. Internet: http://oh.water.usgs.gov/micro/fldsmpl.html/(20 Oct 2006)

49. Why it is advantageous to
study a sample.

50. Generating random numbers.

51. Random Selection is employed when every
member of a population has an equal
chance of being selected to be a member of
the sample.

52. Cluster Sampling is a non-random sampling
technique.

53. Used for granular or powdery samples.

54. To mark out a small area as a sample out of a
large area.

55. Two parallel lines are marked out and individuals
between these lines are recorded.

56. In water sampling.

59. 1) Give one reason why
is it advantageous to
study a sample.
a) Cheaper
b) Faster
c) More Accurate
d) More Comprehensive
Information
2)Give one way of
generating random
numbers.
a) Fishbowl/Lots (with
replacement)
b) Random Number Table
c) Random number
generator in the
calculator or computer.
3) True or False: Random
Selection is employed when
every member of a
population has an equal
chance of being selected to
be a member of the sample.
True
4) True or False: Cluster
Sampling is a non-random
sampling technique.
False.

60. 5) A sampling
technique used for
granular or powdery
samples.
Coning and Quartering
6) A technique used to
mark out a small area
as sample out of a large
area.
Quadrat
7)A sampling
technique where two
parallel lines are
marked out and
individuals between
these lines are
recorded.
Belt Transect.
8-9) Give two considerations in
water sampling.
a. Type of Water body.
b. Tests to be performed on the
sample.
c. Volume of sample
d. Container to use
e. Cleaning procedure for container
f. Water collection technique
g. Transporting and storage
h. How soon to process the
sample.

61. 10) It is a subset of a population on which information is
obtained.
Sample.